I don't have this problem...
Here it what I tried, and it worked perfectly fine !
\documentclass{beamer}
\usepackage[francais]{babel}
\usetheme{Frankfurt}
\begin{document}
\begin{frame}{Outline}
\tableofcontents
\end{frame}
\section{One}
\subsection{Sec 1.1}
\begin{frame}{Title 1}
Hello !
\end{frame}
\begin{frame}{Title 2}
Hello !
\end{frame}
\begin{frame}{Title 3}
Hello !
\end{frame}
\begin{frame}{Title 4}
Hello !
\end{frame}
\begin{frame}{Title 5}
Hello !
\end{frame}
\begin{frame}{Title 6}
Hello !
\end{frame}
\begin{frame}{Title 7}
Hello !
\end{frame}
\begin{frame}{Title 8}
Hello !
\end{frame}
\begin{frame}{Title 9}
Hello !
\end{frame}
\begin{frame}{Title 10}
Hello !
\end{frame}
\begin{frame}{Title 11}
Hello !
\end{frame}
\begin{frame}{Title 12}
Hello !
\end{frame}
\begin{frame}{Title 13}
Hello !
\end{frame}
\begin{frame}{Title 14}
Hello !
\end{frame}
\begin{frame}{Title 15}
Hello !
\end{frame}
\begin{frame}{Title 16}
Hello !
\end{frame}
\section{Two}
\subsection{Sec 2.1}
\begin{frame}{Title 1}
Hello !
\end{frame}
\begin{frame}{Title 2}
Hello !
\end{frame}
\begin{frame}{Title 3}
Hello !
\end{frame}
\begin{frame}{Title 4}
Hello !
\end{frame}
\begin{frame}{Title 5}
Hello !
\end{frame}
\begin{frame}{Title 6}
Hello !
\end{frame}
\begin{frame}{Title 7}
Hello !
\end{frame}
\begin{frame}{Title 8}
Hello !
\end{frame}
\begin{frame}{Title 9}
Hello !
\end{frame}
\begin{frame}{Title 10}
Hello !
\end{frame}
\begin{frame}{Title 11}
Hello !
\end{frame}
\begin{frame}{Title 12}
Hello !
\end{frame}
\begin{frame}{Title 13}
Hello !
\end{frame}
\begin{frame}{Title 14}
Hello !
\end{frame}
\begin{frame}{Title 15}
Hello !
\end{frame}
\begin{frame}{Title 16}
Hello !
\end{frame}
\section{Three}
\subsection{Sec 3.1}
\begin{frame}{Title 1}
Hello !
\end{frame}
\begin{frame}{Title 2}
Hello !
\end{frame}
\begin{frame}{Title 3}
Hello !
\end{frame}
\begin{frame}{Title 4}
Hello !
\end{frame}
\begin{frame}{Title 5}
Hello !
\end{frame}
\begin{frame}{Title 6}
Hello !
\end{frame}
\begin{frame}{Title 7}
Hello !
\end{frame}
\begin{frame}{Title 8}
Hello !
\end{frame}
\begin{frame}{Title 9}
Hello !
\end{frame}
\begin{frame}{Title 10}
Hello !
\end{frame}
\begin{frame}{Title 11}
Hello !
\end{frame}
\begin{frame}{Title 12}
Hello !
\end{frame}
\begin{frame}{Title 13}
Hello !
\end{frame}
\begin{frame}{Title 14}
Hello !
\end{frame}
\begin{frame}{Title 15}
Hello !
\end{frame}
\begin{frame}{Title 16}
Hello !
\end{frame}
\end{document}
And I got this as output :


Maybe if you put a short example, I'see what I can do ...
beamerinstallation is old, this behavior is fixed in recent versions ofbeamer. – Qrrbrbirlbel May 08 '13 at 12:20