Error compacting Mail\x\xxx.nsf: Database is corrupt -- Cannot allocate space

We have a compact -b each night and -B on Sunday and we receivce the error “Error compacting Mail\x\xxx.nsf: Database is corrupt – Cannot allocate space” on a few Databases (10 from 400). The failure occures each night on different databases. As we checked the databases in the morning they are not corrupt.We have Lotus Domino 7.0.3 FP1 on Windows 2003.

Has anyone an idea?