[Tex/LaTex] Beamer, Beamerposter and the TUGraz theme: compilation issue

beamercompiling

When trying to compile using the Beamer class and the TUGraz theme I get the following error message: LaTeX Error: There's no line here to end.
This is in Windows Vista (no goood, I know) with MikTeX 2.9.

When I compile the same with MikTeX 2.9 in Windows XP I have no problem. Why?

PS: I'm using the Beamerposter package.

Here is a MWE:

\documentclass{beamer}
\usetheme{TUGraz} 

\usepackage[orientation=portrait,size=a0,scale=1.4,debug]{beamerposter}

\title{\Huge Some Title\vspace{3mm}}
\author[]{Homer Simpson}

\begin{document}
  \begin{frame}
    \begin{block}{Introducction}
      \begin{itemize}
         \item This is an item.
      \end{itemize}
    \end{block}
  \end{frame}
\end{document}

When I comment the line \usetheme{TUGraz} I have no compilation error.
The TUGraz Beamer-poster theme can be downloaded from here

———————– EDIT ———————————-
And if I try to compile the following code I get Error: Undefined control sequence, referencing the line \end{frame}.

\documentclass[final,hyperref={pdfpagelabels=false}]{beamer}

%%%% Inclusion de fichiers "standalone" %%%%
\usepackage{standalone}

\mode<presentation> {  
  \usetheme{TUGraz}    
}

%%%% Langue française %%%%
\usepackage[english,frenchb]{babel}
\usepackage[latin1]{inputenc}

%%%% Maths and symbols %%%%
\usepackage{amsmath,amsthm, amssymb, latexsym}

%%%% Policies matématiques %%%
\usefonttheme[onlymath]{serif}
\boldmath

%%% Package Beamerposter %%%%
\usepackage[orientation=portrait,size=a0,scale=1.4,debug]{beamerposter}


%%%% Institution %%%%
\institute[ECS-Lab] 
{
  ECS-Lab - ENSEA
    \vspace {3mm}
}

%%%% Titre, auteurs, mails et site web %%%%
\title{\Huge Modes Glissants appliqués au Convertisseur Multicellulaire\vspace{3mm}}
\author[Amet, Ghanes \& Barbot]{Leonardo Amet, Malek Ghanes  et Jean-Pierre Barbot}
\mail{\{leonardo.amet,ghanes,barbot\}@ensea.fr}
\webpage{http://www-ecs.ensea.fr/}

\begin{document}
\begin{frame}
\centering
\begin{block}{Introduction}
\begin{minipage}{0.5\paperwidth}
Les \emph{\textbf{Convertisseurs Multicellulaires}} sont des structures de type \emph{multiniveaux} conçues dans le but de \emph{réduire les tensions sur les interrupteurs de puissance}.
\vspace{5mm}

\begin{minipage}[t]{0.29\paperwidth}
\textbf{Avantages:}
\begin{itemize}
\item réduction de $dV/dt$
\item réduction du contenu harmonique
\item modularité
\item réconfiguration possible (marche dégradée)
\item fréquence aparente de sortie supérieure à la fréquence de commutation
\end{itemize}
\end{minipage}\hspace{2cm}
\begin{minipage}[t]{0.19\paperwidth}
\textbf{Inconvénients:}
\begin{itemize}
\item nombre de composants élevé
\item composants flottants
\item \textbf{\textit{commande de tensions internes}}
\end{itemize}
\end{minipage}
\end{minipage}
\qquad
\begin{minipage}[c]{0.39\paperwidth}
\centering
\textbf{\textit{\large Convertisseur Multicellulaire à 3 cellules}} \vspace{0.6cm}
\hspace{-4cm}
% \scalebox{3.3}{
% \scalefont{0.35}
% \input{schema_multicell}}
\end{minipage}

\centering
\textbf{Pour égaler les tensions supportées par les cellules il faut charger chaque condensateur à une tension spécifique donnée par:
$\displaystyle {V_{C_k} = k\frac{E}{n}}$}
\end{block}

\begin{minipage}{0.479\paperwidth}
\begin{block}{Commande des Tensions Internes}
 \textbf{\color{tugblue} MLI en boucle ouverte:} 

\quad Equilibre naturel des tensions, mais lent et oscilatoire.\vspace{1.1cm}

 \textbf{\color{tugblue} MLI en boucle fermée:}  

\quad Equilibrage plus performant, mais pas suffisament rapide ni robust.\vspace{1.1cm}

\textbf{\color{tugblue} Modes Glissants:} 

\centering 
\quad \textbf{rapide et robust.}\vspace{1.1cm}
 \end{block}
 \end{minipage}
 \quad
\begin{minipage}{0.479\paperwidth}
\begin{block}{Modèle instantané}
Cas d'un Convertisseur Multicellulaire à trois cellules:\vspace{5mm}
\begin{equation*}
\left\{
    \begin{array}{cl}
    \displaystyle   \dot{v}_{_{C_1}}    &= \displaystyle \frac{u_2(t) - u_1(t)}{C_1} \, i_s(t)\\
    \displaystyle   \dot{v}_{_{C_2}}    &= \displaystyle \frac{u_3(t) - u_2(t)}{C_2} \, i_s(t)\\     
    \displaystyle v_s(t) &= \displaystyle \sum_{k=1}^3 [v_{_{C_k}}(t) - v_{_{C_{k-1}}}(t)]u_k(t)
    \end{array}
\right.
\label{eq_mod_inst}
\end{equation*}
\end{block}
\end{minipage}

\begin{block}{Synthèse de la Commande par Modes Glissants}
\vspace{5cm}
\end{block}

\end{frame}
\end{document}

The beginning and the end of the log file are:

    This is pdfTeX, Version 3.1415926-2.3-1.40.12 (MiKTeX 2.9) (preloaded           format=pdflatex 2011.6.19)  25 SEP 2011 21:12
entering extended mode
    .
    .
    .
    Overfull \hbox (50.59032pt too wide) detected at line 38
    [][][] [][][][][][][][][] [][][][][][][][][] [][][][][][][][][] [][][][][][][][
    ][] [][][][][][][] 
     []

    ! Undefined control sequence.
    \beamer@frameslide ...duration=}\thispdfpagelabel 
                                                      {\insertframenumber } \xde...
    l.117 \end{frame}

    ?

Best Answer

The linked theme (TUGraz) has been designed such that an \institute is required. Thus with the minimal example

\documentclass{beamer}
\usetheme{TUGraz} 
\author{Stuff}
\begin{document}
  \begin{frame}
  \end{frame}
\end{document}

an error is seen (plus ones concerning missing colour and logo files which are not relevant to the issue at hand).

Including an \institute fixes the error

\documentclass{beamer}
\usetheme{TUGraz} 
\author{Stuff}
\institute{Stuff}
\begin{document}
  \begin{frame}
  \end{frame}
\end{document}

although the theme should be fixed to check for the presence of the relevant values.

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