long delay at shutdown/reboot

[lucazade]

there is a long delay when shutting down or restarting the system.
it looks like the network-manager service hangs when stopping in init6.

* Asking all remaining processes to terminate... [OK]
* Killing all remaining processes... [fail]
nmdispatcher.action caught signal 15 shutting down ...

If I manually stop the network-manager service before shutdown/restart then everything works fine

this bug is probably related to this old one (solved in 12.04):
https://bugs.launchpad.net/ubuntu/+s...er/+bug/869635

new bug reported:
https://bugs.launchpad.net/ubuntu/+s...r/+bug/1066484