For anyone having the same problem, here is the workaround I am using.
We assume your nfs homes are mounted in /home/nfs.
1) Create a file named "/etc/init.d/killnfs", with the following content:
#!/bin/sh
#
# Script to kill any remaining processes in /home/nfs, and unmount it.
# It should be run after gdm stops.
#
/bin/fuser -km /home/nfs
umount /home/nfs
2) Save it, and then make it executable by running:
chmod 755 /etc/init.d/killnfs
3) Set it to execute on shutown, after gdm stops, by running:
update-rc.d killnfs stop 02 0 6 .
Best regards.
