So, it happened again, not fixed, no surprise.
I am thinking it is an issue with our dear friend Network-Manager, which now appears, according to syslog, to load very early on and thus I suspect is being killed very late on.
When shutting down, if I login to another tty and kill lightdm and then issue the shutdown command, I get the message "Killing All Remaining Processes [Fail]" which indicates the shutdown fails because a process isn't dying.
The following seems to work for me, when you want to shutdown, issue the following to get another tty log in screen:
Log in using your normal log in details.
Kill the new GDM (called lightgdm) by issuing:
Then kill network-manager, because it is a right pita (in all honesty, this might be all you need to do, but the above steps allow you to see all the messages Ubuntu spits out as it shuts down to all you to help debug this issue):
sudo service lightdm stop
Then issue the shutdown command
sudo service network-manager stop
And you should be able to shutdown properly.
sudo shutdown -hP now
Can anyone try this and let me know how it works? It worked for me.
It might also be worth noting I use an encrypted home folder, not sure if that has anything to do with it.
Anyway, I'm off to post a bug on launchpad to get some feedback from the guys in the know.y