You probably just have a bad Nvidia driver, I've had those before. Just a few months ago, my computer would freeze when playing UT. I updated my Nvidia drivers and the problem stopped.
If the problem is very bad, try changing the graphics driver back to the Windows assigned driver and see if the problem still exists; I bet it won't
Another suggestion, try closing everything that you are not using before playing the game. I noticed that my Win XP computer would get the BSOD if i had Kazaa Lite, Trillian, Bandwidth Monitor, Winamp (playing a song) and UT2003 all running at the same time.