This is some foolishness of Windows XP explorer.
a) My colleague zipped a file on his desktop with folder information. Opening on Windows 2000 with Power Archiver was no problem. Opening with explorer where XP displays archives like folders, clicking on "Dokumente und Einstellungen" (documents blah dunno what it's called in english) would make the explorer crash.
b) Same when zipping straße.txt to straße.zip : XP explorer displays the filename inside the archive corrupted!
Conclusions?
1. Using a proper unzipping programm should get rid of those problems. There are freeware one that can be installed without administrator rights.
2. Maybe someone should report the problem to Microsoft and then we all wait for the next Windows update ...