cifs won't shut down

I’m running OpenSUSE 11.0 and have encountered a shutdown problem with cifs. On system shutdown the cifs mounts are busy, with the result that the system hangs on the attempt to unmount them. What can I do about that? It looks to me like a bug.

That happens to me if there’s an error in a mount (in fstab) and also if I change something about the mounted directory while it’s mounted – or indeed change anything related while it’s mounted. Of course, it might be something else too.