Glad the new card is working. Have you tried to overclock it? That could cause BSOD's. Also some people have reported problems with the new Firefox 5.0, try going back to the previous one and see if that helps. Some FF plugins are buggy too.
For your BSOD issues follow this: Blue Screen of Death (BSOD) Posting Instructions
Note: you'll need to post in the Crashes and Debugging forum.
If your original monitor issue is solved, please click the Solved link at the top of any of your posts.