Comment 12 for bug 872472

I saw this on an install of xubuntu 11.10 i386 on a Thinkpad T42 laptop, so I tried booting up the CD and shutting down again. Out of maybe 12 shutdowns it froze 3 times. Intermittent, difficult to reproduce. It looks a lot like bug #628630 - the code that Colin Watson identified there in /etc/init.d/casper do_stop() appears to be the same point where this hangs. And by hang, I don't mean a kernel style hang or freeze, I just mean there is no "Please remove installation" message, but I can switch virtual terminals and hit enter on the console and it gets echoed back. The hang point seems to be (I typed this out on another PC):

The system is going down for halt NOW!
acpid: exiting
Checking for running unattended-upgrades
 * Stopping bluetooth [ OK ]
 * Asking all remaining processes to terminate... [ OK ]
 * Killing all remaining processes... [fail]
modem-manager[1144]: <info> Caught signal 15, shutting down...

nm-dispatcher.action: Caught signal 15, shutting down..
 * Deconfiguring network interfaces... [ OK ]
 * Unmounting temporary filesystems... [ OK ]
 * Deactivating swap... [ OK ]
 * Stopping remaining crypto disks... [ OK ]
 * Stopping early crypto disks... [ OK ]
umount: /run/lock: not mounted

THIS IS WHERE IT HANGS.
IF IT DOESN'T HANG WE GET:

Please remove installation media and close the tray (if any) then press ENTER:
 * Will now halt