Cannot change priority/status/type entries when locale is set

I set my locale to German and imported the translation from this page.

After that I installed Casetracker. When I tried to change entries neither "update" nor "delete" worked, for none of the fields. Changing them directly in the database was my only successful way.
It was pure luck that I found out it was the locale. After I set the locale back to English (to look up the real names of the buttons) I tried it again and it worked.