Try using different versions of Nvidia drivers. I had a laptop with a ATI X600 Mobility Radeon, and found that the 8.12 drivers made video playback extremely unstable resulting in blue screens. Rolling back to the 8.11 drivers completely resolved this issue.
If you are using the latest drivers on an aging graphic chipset, I would suggest trying an earlier version. It just might work, though I am merely guessing that my problem resembles yours. In my experience, Nvidia drivers have been much less problematic than ATI's.