You need to check out the Beamer userguide again.
It only mentions use of \hyperlink (not \hyperref) used in conjunction with \beamergotobutton, or \hypertarget and \beamerbutton.
\documentclass{beamer}
\title{test}
\author{test}
\begin{document}
\maketitle
\begin{frame}
\frametitle{Overview}
\tableofcontents
\end{frame}
\section{first}
\begin{frame}[label=bar]
\frametitle{frame}
Frame, linking to \hyperlink{foo}{\beamergotobutton{A Foo}}
\end{frame}
\begin{frame}[label=foo]
\frametitle{foo}
Bar\par
with a backlink to \hyperlink{bar}{\beamergotobutton{where we came from}}
\end{frame}
\end{document}
You may want to modify the buttons. regards from corporal