I have the same programme setup on a similar system but using an old 1GB Athlon and XP, and it runs fine.
My immediate reaction would be overheating but since CFS3 runs OK it would appear to rule that out.
Have you changed anything else recently? New joystick or something causing a conflict? Maybe your cooling fan isn't working as well as it used to.
Sorry I can't be of more help, but you seem to have covered most things yourself!