BAD_POOL_HEADER is one of those vague errors that could relate to a number of different things.
You might get a bit more of a clue what's wrong if you go to the Event Viewer in Control Panel/Administrator Tools click here
If that doesn't help....
i) if it was a one-off error I wouldn't worry too much about it. It could be just a blip with the updates you installed that have now corrected themselves..
ii) if it's still happening you could try System Restore to put things back to how they were a couple of days ago. Then download/install the updates one at a time to see if it was either of those that were causing the problem.