Well, you made two changes: Added RAM and reduced FPS. So while you know one of those caused the problem, you don't know exactly which one. While adding RAM is always a good thing to help PC performance, my bet is the X1300 is not quite up to the task of running all your clients at a higher FPS. I would spend the next day or two playing with the RAM and your current reduced FPS to make sure your system is stable. After that, then start bringing your FPS up and see if it starts crashing again. If not, congrats! If it does crash then lower your FPS until it stops crashing or buy a new vid card.