Computer is Frozen at the XP Logo

 Models affected: Mostly lab computers (Dell 755 and 760).

We haven't been able to determine what causes this. However, powering off the computer, waiting a 10 seconds, then powering it on again seems to resolve the problem. Note that if you wait less than 10 seconds before pushing the power button to turn on the computer, the machine will do a self test and won't actually power on - you need to push the button again.