Maybe this is an easy one, but I struggled with this now too long :)
I want to have a footnote in a caption of a figure, see the example.
\begin{figure}[!ht]
\caption{a figure caption\footnote{where i got it from}}
\label{somelabel}
\begin{center}
\pgfuseimage{...}
\end{center}
\end{figure}
The compilation error reads as follows
! Argument of \@caption has an extra }.
<inserted text>
\par
l.192 ...i got it from}}
The actual tex code for my figure with the answer of Leo
\pgfdeclareimage[width=6cm]{aba.medcenter}{aba.medcenter}
\begin{figure}[!ht]
\begin{minipage}{\textwidth}
\caption[Medcenter Monthly Medication System]{Medcenter\textsuperscript\textregistered Monthly Medication System\footnote{Quelle Bild: http://www.amazon.com/dp/B000RZPL0M}}
\label{aba.medcenter}
\begin{center}
\pgfuseimage{aba.medcenter}
\end{center}
\end{minipage}
\end{figure}
leads to the error
! LaTeX Error: Command \itshape invalid in math mode.
in the same line. If I comment out the foot note, everything compiles fine. \textsuperscript\texttrademark
isn't the problem, too.