# Problems with undefined reference in beamer [closed]

I have some problems understanding why I get a warning about a undefined reference, which won't go away no matter how many times I compile my document. This has occured in several documents the last week, and always happens when I try to refer to a figure that is more than one frame ahead of the current frame, e.g., I the following is at the end of my file (last frame in sample below is the last frame of the document):

\begin{frame}
\frametitle{Experimental investigations (cont'd)}
\begin{itemize}[<+->]
\begin{itemize}[<+->]
\item Drain-voltage swing almost proportional to the load impedance.
\item Loadlines bend at low drain voltages (increasing load resistance) due to increased knee walk-out induced by shifting of the effective DC operating points of the traps.
\end{itemize}
\begin{itemize}[<+->]
\item No appreciable knee walk-out, which results in undistorted loadlines as device operates in saturation region.
\end{itemize}
\item In both figures, the channel modulation index
$$\beta=(n_\text{s}-n_{\text{s},0})/n_{\text{s},0}\in[-1,0]\text{ for } n_\text{s}\in[0,n_{\text{s},0}]$$
describes the deviation in channel concentration from the equilibrium 2DEG channel concentration ($n_{\text{s},0}$). $n_\text{s}=0$ implies fully depleted 2DEG.
\item Effective trap operating points (squares) correspond to the smallest drain voltage on the loadline which would generate the same average modulation index $\beta$ under DC conditions.
\end{itemize}
\end{frame}

\begin{frame}
\frametitle{Experimental investigations - unpassivated device}
\begin{figure}[ht]
\centering
\caption{RF drain loadlines of unpassivated GaN HEMT with DC and pulsed IV characteristics. Circles denote DC biasing points, squares denote effective DC operating points for the traps.}
\end{figure}
\end{frame}

\begin{frame}
\frametitle{Experimental investigations - passivated device}
\begin{figure}[ht]
\centering
\caption{RF drain loadlines of passivated GaN HEMT with DC and pulsed IV characteristics. Circles denote DC biasing points, squares denote effective DC operating points for the traps.}
\end{figure}
\end{frame}


When I compile the document, all references works just fine, except for the last one with label fig:rf_drain_loadlines_beta_passivated.

LaTeX Warning: Reference fig:rf_drain_loadlines_beta_passivated' on page 1 undefined on input line 319.


The only other warnings in the log are related to unicode-math and microtype, and do not affect the referencing problem. I've tried to compile both with and without using the cleveref package, but without any difference. I've also tried changing the label to something without underscores, but that didn't help either.

Also, I use LuaLaTeX for compiling. If it should matter, my preamble looks like below:

\RequirePackage{atbegshi}
\documentclass[smaller,handout]{beamer}
\usepackage{pgfpages}
\pgfpagesuselayout{2 on 1}[a4paper]

\usefonttheme{professionalfonts}
\mode<presentation>{%
\AtBeginSection{%
}
\useoutertheme[nofootline]{wuerzburg}
\usecolortheme{shark}
\setbeamercovered{transparent}
}
\setbeamertemplate{caption}[numbered]

\usepackage{fontspec}
\usepackage{microtype}
\usepackage{unicode-math}
\usepackage{mathtools}

\usepackage{coursemathLL} % own file with mathematical definitions only
\usepackage{siunitx}
\usepackage{cleveref}


Any hints on what I'm missing here?

-
 Did some more testing now, and it seems like this is coming from the pgfpages package. But what exactly I don't know. – militiaOfDeath Sep 21 '12 at 10:56

## closed as too localized by lockstep, Paul Gaborit, Marco Daniel, tohecz, Paulo CeredaSep 21 '12 at 17:03

This question is unlikely to help any future visitors; it is only relevant to a small geographic area, a specific moment in time, or an extraordinarily narrow situation that is not generally applicable to the worldwide audience of the internet. For help making this question more broadly applicable, see the FAQ.

After deleting all aux` files and everything else one thousand times and recompiling for the one millionth time, it suddenly worked. So most likely nothing to do with pgfpages or any of the other packages that I've loaded.