Perhaps bit of a hack I but could not find another way of unmounting Samba shares automatically before my user session ends. If I do not unmount them myself, they would stay mounted after network manager has shutdown making Ubuntu hang. So to overcome this problem, I’ve done the following:
$ cd /etc/gdm/PostSession
$ sudo vi Default
add your commands before “exit 0″, for example:
...
sudo fusermount -u /home/juraj/shareA/
sudo fusermount -u /home/juraj/shareB/
exit 0
Save (:wq) and give it a go - restart or logoff. Tested in Ubuntu 8.10