The example below is a bit smaller (you don't need to include inputenc to
reproduce the problem).
\documentclass[semhelv]{seminar}
\usepackage[T1]{fontenc}
\begin{document}
\begin{slide}
b \"a z
\end{slide}
\end{document}
cu,
Adrian
--
A "No" uttered from deepest conviction is better and greater than a
"Yes" merely uttered to please, or what is worse, to avoid trouble.
-- Mahatma Ghandi