[Tex/LaTex] Thesis class error Extra } or forgotten \endgroup on second compile (not first) in float caption

captionsfloatsnatbibthesis

I am adapting a paper to a thesis format, and I am getting an error on the second compile of my document (the first one seems to work fine). I am using TeXshop, v. 2.47; I am compiling using pdfTex v.3.1415926-1.40.10 (TeX Live 2009). I have a bibliography in BibTex format and I am using natbib citations. The error message points to the first place that I've included a citation in the caption of a figure.
The error message:

This is pdfTeX, Version 3.1415926-1.40.10 (TeX Live 2009)  \write18
enabled. entering extended mode (./MinExample.tex LaTeX2e <2009/09/24>
Babel <v3.8l> and hyphenation patterns for english, usenglishmax,
dumylang, noh yphenation, german-x-2009-06-19, ngerman-x-2009-06-19,
ancientgreek, ibycus, ar abic, basque, bulgarian, catalan, pinyin,
coptic, croatian, czech, danish, dutc h, esperanto, estonian, farsi,
finnish, french, galician, german, ngerman, mono greek, greek,
hungarian, icelandic, assamese, bengali, gujarati, hindi, kannada ,
malayalam, marathi, oriya, panjabi, tamil, telugu, indonesian,
interlingua, i rish, italian, kurmanji, latin, latvian, lithuanian,
mongolian, mongolianlmc, b okmal, nynorsk, polish, portuguese,
romanian, russian, sanskrit, serbian, slova k, slovenian, spanish,
swedish, turkish, turkmen, ukenglish, ukrainian, upperso rbian, welsh,
loaded. (./duthesis.cls Document Class: duthesis 2008/01/04 v1.0
University of Denver Electronic Thesis  class
(/usr/local/texlive/2009/texmf-dist/tex/latex/setspace/setspace.sty
Package: `setspace' 6.7 <2000/12/01> )
(/usr/local/texlive/2009/texmf-dist/tex/latex/base/report.cls Document
Class: report 2007/10/19 v1.4h Standard LaTeX document class
(/usr/local/texlive/2009/texmf-dist/tex/latex/base/size11.clo)))
(/usr/local/texlive/2009/texmf-dist/tex/latex/graphics/graphicx.sty
(/usr/local/texlive/2009/texmf-dist/tex/latex/graphics/keyval.sty)
(/usr/local/texlive/2009/texmf-dist/tex/latex/graphics/graphics.sty
(/usr/local/texlive/2009/texmf-dist/tex/latex/graphics/trig.sty)
(/usr/local/texlive/2009/texmf-dist/tex/latex/latexconfig/graphics.cfg)
(/usr/local/texlive/2009/texmf-dist/tex/latex/pdftex-def/pdftex.def)))
(/usr/local/texlive/2009/../texmf-local/tex/latex/local/natbib.sty)
(/usr/local/texlive/2009/texmf-dist/tex/latex/amsfonts/amssymb.sty
(/usr/local/texlive/2009/texmf-dist/tex/latex/amsfonts/amsfonts.sty))
(/usr/local/texlive/2009/texmf-dist/tex/latex/oberdiek/epstopdf.sty
(/usr/local/texlive/2009/texmf-dist/tex/latex/oberdiek/epstopdf-base.sty
(/usr/local/texlive/2009/texmf-dist/tex/generic/oberdiek/infwarerr.sty)
(/usr/local/texlive/2009/texmf-dist/tex/latex/oberdiek/grfext.sty)
(/usr/local/texlive/2009/texmf-dist/tex/latex/oberdiek/kvoptions.sty
(/usr/local/texlive/2009/texmf-dist/tex/generic/oberdiek/kvsetkeys.sty
(/usr/local/texlive/2009/texmf-dist/tex/generic/oberdiek/etexcmds.sty)))
(/usr/local/texlive/2009/texmf-dist/tex/generic/oberdiek/pdftexcmds.sty
(/usr/local/texlive/2009/texmf-dist/tex/generic/oberdiek/ifluatex.sty)
(/usr/local/texlive/2009/texmf-dist/tex/generic/oberdiek/ltxcmds.sty))
(/usr/local/texlive/2009/texmf-dist/tex/latex/latexconfig/epstopdf-sys.cfg)))
(./psfig.sty)
(/usr/local/texlive/2009/texmf-dist/tex/latex/caption/caption.sty
(/usr/local/texlive/2009/texmf-dist/tex/latex/caption/caption3.sty))
(/usr/local/texlive/2009/texmf-dist/tex/latex/caption/subcaption.sty)
(./aastex_hack.sty) (./MinExample.aux (./Introduction.aux)
(./Chapter1.aux) (./Chapter2.aux) (./Chapter3.aux))
[1{/usr/local/texlive/2009/texmf-var/fonts/m
ap/pdftex/updmap/pdftex.map}]
(/usr/local/texlive/2009/texmf-dist/tex/latex/base/omscmr.fd) [1]
Underfull \hbox (badness 10000) in paragraph at lines 22--22

[2] (./MinExample.toc
(/usr/local/texlive/2009/texmf-dist/tex/latex/amsfonts/umsa.fd)
(/usr/local/texlive/2009/texmf-dist/tex/latex/amsfonts/umsb.fd) [3])
[4] (./MinExample.lot) [5] (./MinExample.lof

LaTeX Warning: Citation `[' on page vi undefined on input line 5.


LaTeX Warning: Citation `[' on page vi undefined on input line 5.


LaTeX Warning: Citation `[' on page vi undefined on input line 5.

! Extra }, or forgotten \endgroup. <argument> ...ider it to be very
reliable.\relax }
                                                   l.5 ...onsider it to be very reliable.\relax }}{2}
                                                   ?

Here is my minimized preamble and master document:

\documentclass[11pt,lot,lof]{duthesis} \usepackage[pdftex]{graphicx}

\usepackage{natbib} \usepackage{amssymb} \usepackage{epstopdf}
\usepackage{psfig} \usepackage{caption} \usepackage{subcaption}
\usepackage{deluxetable} \usepackage{aastex_hack} \def\mic{$\mu$m$\;$}

\includeonly{Chapter3} \title{Theis title} \submitted{2013}
\author{David Tennant} \advisor{The Master} \abstract {abstract}

\begin{document}

\include{Introduction} \include{Chapter1} \include{Chapter2}
\include{Chapter3}

\end{document}

Then in Chapter3.tex:

\chapter{Interferometric Study of Wolf-Rayet stars}

\begin{figure}[htb]

\centering

\includegraphics[scale=0.8]{Fig1}

\caption{Our attempts to reproduce the wideband data with a binary
orbit for WR 137. Both binary models adopted the values of
\citet{2005MNRAS.360..141L}; the missing angular parameter ($\Omega$ ,
longitude of the Ascending Node) was varied to find the best fit to
the Position Angle and separation derived from interferometric
measurements at a particular phase in two cases.  The resulting models
are shown for \citealt{2010RMxAC..38...54R}, yielding
$\Omega=112\degr$, and the value that best agrees with our data,
$\Omega=137\degr$.  Both agree with the separations predicted by
\citealt{2005MNRAS.360..141L} to within their published error bars.
The data point from PTI's NW baseline was taken in poor weather
conditions, so we do not consider it to be very reliable.}
\label{wr137wb}

\end{figure}

Fig1 is an eps file, which worked in the document I submitted for publication, so I don't think there's a problem with it.
The duthesis class file looks like this:

\NeedsTeXFormat{LaTeX2e} \ProvidesClass{duthesis}
         [2008/01/04 v1.0 University of Denver Electronic Thesis class]

\RequirePackage{setspace}

\newcounter{subyear}

\setcounter{subyear}{\number\year}

\def\submitted#1{\gdef\@submitted{#1}}
\def\advisor#1{\gdef\@advisor{#1}}

\def\@submittedyear{\ifnum\month>10 \stepcounter{subyear}\thesubyear  
\else\thesubyear\fi}

\def\@submittedmonth{\ifnum\month>10 January\else\ifnum\month>5
November   \else June\fi\fi}

\long\def\@abstract{\@latex@error{No \noexpand\abstract given}\@ehc}

\newcommand*{\frontmatter}{   \pagenumbering{roman}  }

\newcommand*{\mainmatter}{\pagenumbering{arabic}}
\newcommand*{\makelot}{} \newcommand*{\makelof}{}
\newcommand*{\makelos}{}

\newcommand*{\begincmd}{ \doublespacing \maketitlepage \frontmatter
\makecopyrightpage \makeabstract \makededication
\clearpage\makeacknowledgements %\makeapprovalpage
\begin{spacing}{1.0} \tableofcontents \clearpage \makelot \clearpage
\makelof \clearpage \makelos \end{spacing}

\mainmatter } %bibliography and appendix goes in your file
\newcommand*{\DUendcmd}{ \newpage
\addcontentsline{toc}{chapter}{Bibliography} \bibliographystyle{apj}
\bibliography{bibdatabase} %\clearpage
%\addcontentsline{toc}{chapter}{Appendix} %\section*{\Huge{Appendix
1}} \input{Appendices} } \AtBeginDocument{\begincmd}
\AtEndDocument{\DUendcmd}


\def\@submitted{\@submittedmonth~\@submittedyear}
\def\@division{Natural Sciences and Mathematics} \def\@dept{Physics
and Astronomy} \def\@deptpref{Department of }
\def\departmentprefix#1{\gdef\@deptpref{#1}}
\def\department#1{\gdef\@dept{#1}}
\long\def\acknowledgements#1{\gdef\@acknowledgements{#1}}
\def\dedication#1{\gdef\@dedication{#1}}

\newcommand{\maketitlepage}{{   \thispagestyle{empty}   \sc  
\vspace*{0in}   \begin{center}   \@title   \end{center}  
\vspace{.3in}   \begin{center}
    A Dissertation \\
    Presented to the Faculty \\
    of \@division \\
    University of Denver   \end{center}   \vspace{.3in}   \begin{center}   in Partial fulfillment  \\
    of the Requirements for the Degree \\
    of Doctor of Philosophy   \end{center}   \vspace{.3in}   \begin{center}
          by \\
    \@author \\
    \@submitted \\
    Advisor: \@advisor   \end{center}   \clearpage   }}

\newcommand{\makeabstracttitlepage}{{   \thispagestyle{empty}   \sc  
\vspace*{0in}   \begin{center}
    \LARGE \@title   \end{center}   \vspace{.3in}   \begin{center}
    An Abstract of a Dissertation \\
    Presented to the Faculty \\
    of \@division \\
    University of Denver   \end{center}   \vspace{.3in}   \begin{center}   in Partial fullfillment  \\
    of the Requirements for the Degree \\
    of Doctor of Philosophy   \end{center}   \vspace{.3in}   \begin{center}
          by \\
    \@author \\
    \@submitted \\
    Advisor: \@advisor   \end{center}   \clearpage   }}

\newcommand{\makeapprovalpage}{{   \thispagestyle{empty}  
\vspace*{0in}   \begin{center}   \sc{   \large{
    Graduate Studies \\
    At \\
    The University of Denver}}   \end{center}   \vspace{.3in}   \small   \noindent Upon the recommendation of the chairperson of the \@deptpref
\@dept { }this dissertation is   hereby accepted in partial
fulfillment of the requirements for the degree of \\
    \begin{center}  Doctor of Philosophy   \end{center}   \vspace{.3in}   \flushright   \begin{minipage}{2.5in}   \begin{center}
~\hrulefill \\ \vspace{-.065in}   Professor in charge of dissertation
\\ ABC\\   \vspace{1in}
    ~\hrulefill \\   Dissertation Committee Members \\   ~\hrulefill \\   X\\   Y\\   Z\\   \vspace{1in} ~\hrulefill \\ \vspace{-.06in}  
Vice Provost for Graduate Studies \\   \end{center}    \end{minipage} 
\vspace{.5in}   \flushleft   \begin{minipage}{1.5in}   \begin{center}
~\hrulefill \\ \vspace{-.06in}   Date \\   \end{center}  
\end{minipage}   \clearpage   }}

\newcommand*{\makecopyrightpage}{   \thispagestyle{empty}  
\vspace*{0in}   \begin{center}
    \copyright\ Copyright by \@author, \number\year. \\
    All Rights Reserved   \end{center}   \clearpage   } \def\makededication{   \ifx\@dedication\undefined   \else
    \vspace*{3in}    \begin{center}
    \@dedication \end{center}

    \clearpage   \fi   }      \newcommand*{\quotationpage}{   \thispagestyle{empty}   \vspace*{0in} \begin{flushright}
{\Large{Endings...}}  \end{flushright}    \end{flushright}
\begin{flushright} Quotation \end{flushright}   \clearpage   }
\newcommand*{\makeabstract}{   \newpage   %\thispagestyle{empty}  
\setstretch{1.0}
    \noindent Author: \@author\newline   Title:  \@title\newline   Advisor: \@advisor \newline   Degree Date: \@submitted\newline
       \begin{center}
           \Large \textbf{Abstract}
    \end{center}
    \setstretch{1.6434}
    \@abstract   \clearpage   }


\def\makeacknowledgements{   \ifx\@acknowledgements\undefined   \else
    \addcontentsline{toc}{section}{Acknowledgements}
    \begin{center}
      \Large \textbf{Acknowledgements}
    \end{center}
    \@acknowledgements
    \clearpage   \fi   }

\DeclareOption{lot}{\renewcommand*{\makelot}{  
\addcontentsline{toc}{section}{List of Tables}\listoftables}}  
\DeclareOption{lof}{\renewcommand*{\makelof}{  
\addcontentsline{toc}{section}{List of Figures}\listoffigures}}
\DeclareOption{los}{   \renewcommand*{\makelos}{
    \RequirePackage{losymbol}
    \section*{List of Symbols\@mkboth {LIST OF SYMBOLS}{LIST OF SYMBOLS}}
    \@starttoc{los}
    \addcontentsline{toc}{section}{List of Symbols}   } }

\DeclareOption*{\PassOptionsToClass{\CurrentOption}{report}}
\ProcessOptions

\LoadClass[11pt]{report} \setlength{\rightmargin}{1.25in}
\setlength{\leftmargin}{1.00in} \setlength{\oddsidemargin}{0.75in}
\setlength{\evensidemargin}{0.75in} %\setlength{\topmargin}{1.25in}
%\setlength{\bottommargin}{1.25in} %\setlength{\oddsidemargin}{.5in}  
%{.4375in} %\setlength{\evensidemargin}{.5in} %{.4375in}
\setlength{\topmargin}{-.25in}  %{-.5625in}
\setlength{\textheight}{8.25 in} \setlength{\textwidth}{5.5in}

\long\def\abstract#1{\gdef\@abstract{#1}}



\endinput

%%  %% End of file `duthesis.cls'.

and the aastex_hack.sty is just a list of symbols and abbreviations

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Bibliography stuff from aastex.cls
%% lines 1551-1648
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\let\jnl@style=\rmfamily 
\def\ref@jnl#1{{\jnl@style#1}}% 
\newcommand\aj{\ref@jnl{AJ}}% Astronomical Journal 
\newcommand\araa{\ref@jnl{ARA\&A}}% Annual Review of Astron and Astrophys 
\newcommand\apj{\ref@jnl{ApJ}}% Astrophysical Journal 
\newcommand\apjl{\ref@jnl{ApJ}}% Astrophysical Journal, Letters 
\newcommand\apjs{\ref@jnl{ApJS}}% Astrophysical Journal, Supplement 
\newcommand\ao{\ref@jnl{Appl.~Opt.}}% Applied Optics 
\newcommand\apss{\ref@jnl{Ap\&SS}}% Astrophysics and Space Science 
\newcommand\aap{\ref@jnl{A\&A}}% Astronomy and Astrophysics 
\newcommand\aapr{\ref@jnl{A\&A~Rev.}}% Astronomy and Astrophysics Reviews 
\newcommand\aaps{\ref@jnl{A\&AS}}% Astronomy and Astrophysics, Supplement 
\newcommand\azh{\ref@jnl{AZh}}% Astronomicheskii Zhurnal 
\newcommand\baas{\ref@jnl{BAAS}}% Bulletin of the AAS 
\newcommand\jrasc{\ref@jnl{JRASC}}% Journal of the RAS of Canada 
\newcommand\memras{\ref@jnl{MmRAS}}% Memoirs of the RAS 
\newcommand\mnras{\ref@jnl{MNRAS}}% Monthly Notices of the RAS 
\newcommand\pra{\ref@jnl{Phys.~Rev.~A}}% Physical Review A: General Physics 
\newcommand\prb{\ref@jnl{Phys.~Rev.~B}}% Physical Review B: Solid State 
\newcommand\prc{\ref@jnl{Phys.~Rev.~C}}% Physical Review C 
\newcommand\prd{\ref@jnl{Phys.~Rev.~D}}% Physical Review D 
\newcommand\pre{\ref@jnl{Phys.~Rev.~E}}% Physical Review E 
\newcommand\prl{\ref@jnl{Phys.~Rev.~Lett.}}% Physical Review Letters 
\newcommand\pasp{\ref@jnl{PASP}}% Publications of the ASP 
\newcommand\pasj{\ref@jnl{PASJ}}% Publications of the ASJ 
\newcommand\qjras{\ref@jnl{QJRAS}}% Quarterly Journal of the RAS 
\newcommand\skytel{\ref@jnl{S\&T}}% Sky and Telescope 
\newcommand\solphys{\ref@jnl{Sol.~Phys.}}% Solar Physics 
\newcommand\sovast{\ref@jnl{Soviet~Ast.}}% Soviet Astronomy 
\newcommand\ssr{\ref@jnl{Space~Sci.~Rev.}}%          % Space Science Reviews 
\newcommand\zap{\ref@jnl{ZAp}}% Zeitschrift fuer Astrophysik 
\newcommand\nat{\ref@jnl{Nature}}% Nature 
\newcommand\iaucirc{\ref@jnl{IAU~Circ.}}% IAU Cirulars 
\newcommand\aplett{\ref@jnl{Astrophys.~Lett.}}% Astrophysics Letters 
\newcommand\apspr{\ref@jnl{Astrophys.~Space~Phys.~Res.}}% Astrophysics Space Physics Research 
\newcommand\bain{\ref@jnl{Bull.~Astron.~Inst.~Netherlands}}% Bul. Astr. Inst. of the Netherlands 
\newcommand\fcp{\ref@jnl{Fund.~Cosmic~Phys.}}% Fundamental Cosmic Physics 
\newcommand\gca{\ref@jnl{Geochim.~Cosmochim.~Acta}}% Geochimica Cosmochimica Acta 
\newcommand\grl{\ref@jnl{Geophys.~Res.~Lett.}}% Geophysics Research Letters 
\newcommand\jcp{\ref@jnl{J.~Chem.~Phys.}}% Journal of Chemical Physics 
\newcommand\jgr{\ref@jnl{J.~Geophys.~Res.}}% Journal of Geophysics Research 
\newcommand\jqsrt{\ref@jnl{J.~Quant.~Spec.~Radiat.~Transf.}}% Journal of Quantitiative Spectroscopy and Radiative Trasfer 
\newcommand\memsai{\ref@jnl{Mem.~Soc.~Astron.~Italiana}}% Mem. Societa Astronomica Italiana 
\newcommand\nphysa{\ref@jnl{Nucl.~Phys.~A}}% Nuclear Physics A 
\newcommand\physrep{\ref@jnl{Phys.~Rep.}}% Physics Reports 
\newcommand\physscr{\ref@jnl{Phys.~Scr}}% Physica Scripta 
\newcommand\planss{\ref@jnl{Planet.~Space~Sci.}}% Planetary Space Science 
\newcommand\procspie{\ref@jnl{Proc.~SPIE}}% Proceedings of the SPIE 
\newcommand\pasa{\ref@jnl{PASA}} % Publications of the Astron. Soc. of Australia
\newcommand\nar{\ref@jnl{New A Rev.}} % New Astronomy Review


\let\astap=\aap 
\let\apjlett=\apjl 
\let\apjsupp=\apjs 
\let\applopt=\ao 

%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Symbols from aastex.cls
%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%
%% lines 1649-1771
%%%%%%%%%%%%%%%%%%%%%%%%%%
\newcommand\phn{\phantom{0}}% 
\newcommand\phd{\phantom{.}}% 
\newcommand\phs{\phantom{$-$}}% 
\newcommand\phm[1]{\phantom{#1}}% 
\let\la=\lesssim            % For Springer A&A compliance... 
\let\ga=\gtrsim 
%\newcommand\sq{\mbox{\rlap{$\sqcap$}$\sqcup$}}% 
\newcommand\arcdeg{\mbox{$^\circ$}}% 
%\newcommand\arcmin{\mbox{$^\prime$}}% 
%\newcommand\arcsec{\mbox{$^{\prime\prime}$}}% 
\newcommand\fd{\mbox{$.\!\!^{\mathrm d}$}}% 
\newcommand\fh{\mbox{$.\!\!^{\mathrm h}$}}% 
\newcommand\fm{\mbox{$.\!\!^{\mathrm m}$}}% 
\newcommand\fs{\mbox{$.\!\!^{\mathrm s}$}}% 
\newcommand\fdg{\mbox{$.\!\!^\circ$}}% 
\newcommand\farcm@mss{\mbox{$.\mkern-4mu^\prime$}}% 
\let\farcm\farcm@mss 
\newcommand\farcs@mss{\mbox{$.\!\!^{\prime\prime}$}}% 
\let\farcs\farcs@mss 
\newcommand\fp{\mbox{$.\!\!^{\scriptscriptstyle\mathrm p}$}}% 
\newcommand\micron{\mbox{$\mu$m}}% 
\def\farcm@apj{% 
 \mbox{.\kern -0.7ex\raisebox{.9ex}{\scriptsize$\prime$}}% 
}% 
\def\farcs@apj{% 
 \mbox{% 
  \kern  0.13ex.% 
  \kern -0.95ex\raisebox{.9ex}{\scriptsize$\prime\prime$}% 
  \kern -0.1ex% 
 }% 
}% 
\newcommand\case[2]{\mbox{$\frac{#1}{#2}$}}% 
\newcommand\slantfrac{\case}% 
\newcommand\onehalf{\slantfrac{1}{2}}% 
\newcommand\onethird{\slantfrac{1}{3}}% 
\newcommand\twothirds{\slantfrac{2}{3}}% 
\newcommand\onequarter{\slantfrac{1}{4}}% 
\newcommand\threequarters{\slantfrac{3}{4}}% 
\newcommand\ubvr{\mbox{$U\!BV\!R$}}%% UBVR system 
\newcommand\ub{\mbox{$U\!-\!B$}}%   % U-B 
\newcommand\bv{\mbox{$B\!-\!V$}}%   % B-V 
\newcommand\vr{\mbox{$V\!-\!R$}}%   % V-R 
\newcommand\ur{\mbox{$U\!-\!R$}}%   % U-R 
\newcommand\ion[2]{#1$\;${\small\rmfamily\@Roman{#2}}\relax}% 
%%%%\newcommand\nodata{ ~$\cdots$~ }% 
\newcommand\diameter{\ooalign{\hfil/\hfil\crcr\mathhexbox20D}}% 
\newcommand\degr{\arcdeg}% 
\newcommand\Sun{\sun}% 
\newcommand\Sol{\sun}% 
\newcommand\sun{\odot}% 
\newcommand\Mercury{\astro{\char1}}% Mercury symbol, "1" 
\newcommand\Venus{\astro{\char2}}% Venus symbol, "2" 
\newcommand\Earth{\earth}% 
\newcommand\Terra{\earth}% 
\newcommand\earth{\oplus}% 
\newcommand\Mars{\astro{\char4}}% Mars symbol, "4" 
\newcommand\Jupiter{\astro{\char5}}% Jupiter symbol, "5" 
\newcommand\Saturn{\astro{\char6}}% Saturn symbol, "6" 
\newcommand\Uranus{\astro{\char7}}% Uranus symbol, "7" 
\newcommand\Neptune{\astro{\char8}}% Neptune symbol, "8" 
\newcommand\Pluto{\astro{\char9}}% Pluo symbol, "9" 
\newcommand\Moon{\astro{\char10}}% Moon symbol, "M" 
\newcommand\Luna{\Moon}% 
\newcommand\Aries{\astro{\char11}}% 
\newcommand\VEq{\Aries}% vernal equinox (Aries) 
\newcommand\Taurus{\astro{\char12}}% 
\newcommand\Gemini{\astro{\char13}}% 
\newcommand\Cancer{\astro{\char14}}% 
\newcommand\Leo{\astro{\char15}}% 
\newcommand\Virgo{\astro{\char16}}% 
\newcommand\Libra{\astro{\char17}}% 
\newcommand\AEq{\Libra}% autumnal equinox (Libra) 
\newcommand\Scorpius{\astro{\char18}}% 
\newcommand\Sagittarius{\astro{\char19}}% 
\newcommand\Capricornus{\astro{\char20}}% 
\newcommand\Aquarius{\astro{\char21}}% 
\newcommand\Pisces{\astro{\char22}}% 
\def\load@astro{% 
 \dimen@=1\aas@ptsize\p@ 
 \font\astro@font=Astrosym at\dimen@ 
}% 
\def\astro#1{\leavevmode\hbox{\astro@font#1}}% 
\def\astro@font{% 
 \ClassWarning{aastex}{% 
  Please use class option `astro', since you are using the astro font.% 
 }% 
}% 
\newcommand\sbond{\chem@bnd{\@sbnd}}% 
\newcommand\dbond{\chem@bnd{\@dbnd}}% 
\newcommand\tbond{\chem@bnd{\@tbnd}}% 
\def\chem@bnd#1{% 
 {% 
  \kern.1em\relax 
  \setbox\z@\hbox{M}% 
  \dimen@ii.8em\relax 
  \p@=.1em\relax 
  \dimen@.5\ht\z@\dimen@i-\dimen@ 
  \advance\dimen@1.5\p@\advance\dimen@i-1.0\p@ 
  #1% 
  \kern.1em\relax 
  }% 
 }% 
\def\@sbnd{% 
 \advance\dimen@-1.5\p@\advance\dimen@i1.5\p@ 
 \vrule\@height\dimen@\@depth\dimen@i\@width\dimen@ii\nobreak 
 }% 
\def\@dbnd{% 
 \advance\dimen@-0.5\p@\advance\dimen@i0.5\p@ 
 \vrule\@height\dimen@\@depth\dimen@i\@width\dimen@ii\nobreak 
 \advance\dimen@-1.5\p@\advance\dimen@i1.5\p@ 
 \hskip-\dimen@ii 
 \vrule\@height\dimen@\@depth\dimen@i\@width\dimen@ii\nobreak 
 }% 
\def\@tbnd{% 
 \vrule\@height\dimen@\@depth\dimen@i\@width\dimen@ii\nobreak 
 \advance\dimen@-1.5\p@\advance\dimen@i1.5\p@ 
 \hskip-\dimen@ii 
 \vrule\@height\dimen@\@depth\dimen@i\@width\dimen@ii\nobreak 
 \advance\dimen@-1.5\p@\advance\dimen@i1.5\p@ 
 \hskip-\dimen@ii 
 \vrule\@height\dimen@\@depth\dimen@i\@width\dimen@ii\nobreak 
 }%

Sorry if this is too much information, this is my first post and I want to be thorough.

Best Answer

As your problem appears only on the second run it is something that got broken when it as written out to the "lof" (list of figures) file in the first run. This is normally due to a fragile command in a caption and seeing the warnings

LaTeX Warning: Citation `[' on page vi undefined on input line 5.

prior to the error most likely the citation commands in the caption are the culprit. So without further checking my guess is that adding \protect in front of \citet and/or \citealt wil resolve this issue.

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