Adam, Helen, Ann and anyone who's interested,

the problem is solved.

Even though the VSC service was disabled the problem persisted since
they use Veritas for backup and this is starting the vssvc.exe directly.

So diabling the service didn't cure the problem, but disabling the
backup for this machine did the trick.

Until now I made the experience that backup software is not touching
files with a lock on them...


Luc.