Comment 30 for bug 882817

The trick for me to solve this issue was to manually unmount an nfs share I put in /etc/fstab before rebooting/halting the system.
Thanks rupert for pointing this out at #29

For information, the mouting point I defined is 192.168.1.20:/srv/nfs/ubuntu-11.10-desktop /media/nfs nfs ro 0 0 and i use it for tftp server.