Hi, I have a similar problem and I have been trouble shooting for 2 weeks. I finally found out that it was my Nvidia VGA Card (8800GTX).
You can do one thing- Disable your Nvidia driver and use VGA driver and see if this helps. My BSODs were gone when I used VGA driver to check. You can use VGA driver and also setup Driver Verifier to speed up process. If you don't get any BSODs with Nvidia Driver unsinstalled and Driver Verifier on then you know the problem.