automounted directry was not accessible.

Yesterday a colleague transfered an NFS shared directory on a linux box.
Our two sunray servers are running without reboot. On one sunray server
the directory mounted via automount ( map's are shared via NIS ) was available,
on the other server it was not accessible.

Today I checked it again.
fuser /sdk

didn't reveal any user, so I did a
umount -f /sdk

and after this an
ls /sdk

showed the content again.

On the second box where still some users logged in. I suppose, that the directory was still in use somewhere.