Hi everyone, just finished hunting this bug myself.It seems that it was caused by a bad entry in the mime.magic file of libmagic1. This issue is tracked by #379042 (which got fixed a few versions before the package entered etch).
By the way, #335179 (which is already archived) seems to have the very same cause.
Please close/merge/archive/whatever #326822 (i am not a DD and don't know what is the proper thing to do).
Regards, Stefan