Sorry for the late response. I checked while playing, and the card never went over 65°C.
Ok heat isnt an issue at all then, the next thing it could possiably be is the card is wanting more power but it isnt getting it, do you have a sufficient psu to power everything and still have around 50W spare??
Only other thing. Can think of is a driver issue or possiably somthing to do with windows that interupts ur cpu/gpu whileur playing for a certian amoun of time.