Have you deleted the Quarantined file?
The most probable reason is that the language setting got tweaked and the language changed to one that uses characters not supported by your comp.
You have to find the View tab (2nd Tab if I'm not mistaken).
Read this thread:
http://www.gnutellaforums.com/showth...+cannot+german (sorry, I'm too lazy at this moment to do more...)
Cheers