I have had that happen before, my anti-virus scanned and somehow that took enough resources from my CPU to force-close my game. --- " For things like online passes, make a better game and people wont trade it in." - Todd Howard
My vanilla Skyrim did that all the time (well not frequently but it was a big cause of my over-zealous use of quicksaves). I found it too funny that my game was there one second and without blinking I was all of a sudden staring at my desktop without so much as a screen flash or anything to trigger the recognition of a transition from program to nothing to actually be mad about it.
Still find it amazing how well Skyrim crashes: so smooth. --- DWO - Wei - from Yong Chang
I get it occasionally, I just assume it's the crashes associated with playing a game by Bethesda. I've never played a Bethesda game that didn't have random, unexplainable CTDs. At least Skyrim is far better than Fallout 3 and New Vegas were.
If you start getting them a lot, like every 30 minutes or less, then you've probably got a problem. Otherwise it's probably nothing worth worrying about. --- http://img714.imageshack.us/img714/1797/fella.jpg