It seems that clamd has absolutely no rights to scan an single file on my server. Disabling AppArmor does not help. I've tried both "/etc/init.d/apparmor stop" and "/etc/init.d/apparmor teardown". I restarted clamd too ofcourse.
the file permissions are ok (I'm testing on a world writable file).
and no, using clamscan instead of clamdscan is not an option... I'm calling clamd via a python script (using the pyclamd module). The result are identical when I scan the file via my script or via clamdscan.
SELinux is not installed (I think). Not sure how I can verify this on Ubuntu 13.10...