Windows Servers after automatic updates, restart problem

Hello.

I have been having reboot problems with Windows Servers after Automatic
Updates.
When the servers finish the updates installations which require an automatic
restart of the servers, the servers get stuck at shutdown. The only recourse
is to do a hard shutdown of the servers and power them back up.

The affected server versions are Windows Server 2000, 2003, and 2003 R2. All
the servers are domain members of 2003 R2 Active Directory. The update
installation policy is applied by group policy and updates are deployed using
WSUS.

The strange thing about this problem is that not every server is affected. I
manage over 50 servers and more than half on them are affected. You can
imagine the chaos this problem has caused when the servers do not come back
up after the restart.

I think this problem have started more than half a year ago. To my dismal, I
cannot find the cause of the problem or the commonality of the servers that
are affected.

If anyone has an idea of what can be causing this problem, let me know.

Thank you.