Windows hangs during shutdown

After upgrading our clients to 12.1.6 MP5, we started having problems with Windows Updates.  After installing Windows patches, and initiating a reboot to complete the install, the PC would hang during the shutdown phase of the reboot.

This is not happening on every PC.  And I was only able to reproduce it once on my test PC.

I found several references in this forum to the same issue:

http://www.symantec.com/connect/forums/sep-client-...

http://www.symantec.com/connect/forums/windows-7-h...

Is anyone else experiencing this issue?

Thanks !