I'd try to eliminate things one by one, and I'd start with GFX drivers myself.
What I personally would do, is remove the GFX drivers, then install the ones that came with the GFX card and see how it goes.
Same with audio/lan drivers if the GFX didn't solve anything . . . in fact reinstall all Mobo drivers from the disc that came with it . . just to hopefully eliminate driver issues from the problem.
Did you install any software on or about the time of the Windows update, giving a possible conflict somewhere?
I used to run Avast antivirus for years, but when I updated to Win 7 ultimate it caused BSOD randomly . . took a while to fathom it out . . no problems since binning Avast . . bloody computers
