Your crashing on cpu intensive stuff probably has it's root issue in heat.  Crack the case open and make sure your cpu fan and heatsink are nice and free from dust and the other assorted crap that gets sucked into your computer.  That's just a short term fix though.  I have a phenom quad core too(9800gtx) that just plain doesn't cut it anymore.   The twin core in my wife's laptop renders faster than this thing.  So, I know how you feel with the whole issue.