Shutdown problems after autoupdate

I am using XP Pro SP1. After autoupdating, my computer will not shutdown. It does not matter if I choose to reboot immmediately after the update when prompted or manually shutdown later. As an experiment, I will be performing the next update manually to see if the same issue occurs.

Any clues?

Do you have installed all the updates/patches for xp? Also updated all drivers for your cards and devices?