Comment 11 for bug 1124803

kernel
3.8.3-030803-generic #201303141650 SMP Thu Mar 14 20:58:52 UTC 2013 i686 i686 i686 GNU/Linux
network-manager:
  Installed: 0.9.8.0-0ubuntu2
and related libnm* and libnl* libraries from raring
on the top of 12.10 quantal

The system shuts down correctly. Although I have not tried x86_64.

Ernie, I can only suggest to try
sudo stop network-manager
and check
ls -l /run/sendsigs.omit.d/
should be no files related to neworkmanager
ps axw | grep -ie '\(netw\|dhcl\|dns\)'

Have you tried any workarounds or debug scripts from similar bugs
(/etc/init.d/networking, some new jobs in /etc/inti,
scripts to save list of open files and running processes, etc.)?

Perhaps, there is something meaningful in the very last messages.
Try to login from a tty ([Ctrl+Alt+F1]),
sudo halt
and press [Ctrl+Alt+F1] again to suppress plymouth image.

The next step would be rising upstart log-priority.