A fresh windows install would pretty much rule out any software issues. If you do a fresh install and it's stable, then you know you have a software problem.
If your memory is running at 1600, turn it down to 1333 and see if that fixes your instability.
Punkbuster is an anti-cheat/hack program that has been known to cause stability problems. It installs whenever you install Bad Company 2 and Crysis (original) and some others. If you have it installed, remove it and see if that helps.