If I use umlauts in the glossary label, LaTeX does throw a lot of exceptions, one of them:
Missing \endcsname inserted. ...lgröße}{name={},plural={},description={}}
MWE:
\documentclass[pdftex]{scrreprt}
\usepackage[utf8]{inputenc}
\usepackage[]{glossaries}
\newglossaryentry{Zielgröße}{name={},plural={},description={}}
EDIT: How can I get the glossary to work with umlauts?