I had the same problem. This is what helped on my AMD 64 System (3800+): I had to turn down Hyper transport from 4x to 1x. This results in a speed loss of around 5% but since I've done that BF2 runs stable! So most likely it is some sort of a memory problem caused by punkbuster because pb is scanning your memory regularly and causes your computer to crash if the memory is not configured properly
Good luck!
Good luck!