I bought the aforementioned GPU just recently replacing my 9800GT 512mb Green Edition which went unresponsive. Thing is the new one is according to Speedfan is running at 76-80C on idle and around 100-110C while gaming. At first the temperature would even gradually go up on idle over time. I fixed that by replacing the thermal grease which honestly looked quite ancient to the point of non-existence so now the temperatures are consistent around the previously mentioned numbers. It worked fine like that for a few days but now it seems that it tends to fail at 80C as just today I had it shut down suddenly. Afterwards I ejected the card and let it cool off the reinserted it and now it seems to be working as previously (at 76-80C idle etc.).
I've thought about replacing the fan since it looks fairly weak but I'm wondering if the PSU would be at fault instead or maybe something else. So I eventually thought I'd ask for advice here before I fork over more cash for something.