Vista bluescreen only while locked

I've been running Vista 32bit for a few weeks now and it was fine for the first couple weeks. Now whenever I leave it Locked for awhile, a few hours or more, I come back and it tells me that it has blue screened. I was using Sleep and I read that there is a problem with Sleep and blue screens under Vista, so I turned it off but it continues to blue screen while locked and idle.

Everything is running at stock speeds and my cooling is fine, drivers are all up to date as well. Anyone know what could be causing this?

http://img184.imageshack.us/img184/4938/taskmanrp8.jpg

That is generally what is running anytime that it bluescreens. Vista has been updated to SP1 and I've got all the latest updates.

I've never seen it bluescreen while I am on the computer, only when I come back it has been restarted and tells me it bluescreened.

If it helps here are my system specs

Asus P5K Deluxe
Q6600 @ stock speed
2x 2gb sticks of OCZ PC6400
9800GTX @ stock speeds
600W OCZ PSU

I believe I have figured out what was causing it.

I found out they were all USB related bluescreens and for some reason having a 360 wireless controller adapter plugged into my monitor's USB port would cause it. Ever since plugging it into a port on my motherboard the problem has gone away.