Issue with radeon hd 4870 x2 videocard overheating.

have you tried manual fan control with ccc or msi afterburner?

or just monitoring the temps to verify they are actually shooting up to 90c+ to cause a shut-down? And you didn't say, but I'd assume you formatted everything with the new hardware... may try it again with new drivers.

otherwise, have you used any other cpu temp monitors to make sure it's not causing the shutdowns instead?

Also, I know my old 295gtx got real hot after a few years of use, and taking it apart to re-apply thermal paste to the gpu/memory after all the dust and heat cooking it pretty good over time.

i did a fresh re-format, and i have monitored it basically because I am using my onboard atm and its completely fine, been on for days without any issues, its most definitly overheating, just tried blowing all the dust out, gonna give it another shot, id just hate to have to throw this 1 away since its still a really nice card ;D

Ihave same problem same card over heats bad, then the computer shuts downs. I watched it with my infared camera the video card gets so hot the heat spreads into the mother board and up to the cpu then the computer shuts off. I have Core I7 and 2 Radeon HD 4870 cross fire. It has done this since it was new. I use to ATI Catalyst Control Center to manually run the fans at 100% and it still runs hot at 96 degrees C. Way to hot and this is BS cards cost alot of money and the manufacture blames everything on the power supply and bla bla BS I have tired other power supplies and nothing helps. Many other people are having the same problem with this card they should recall it because it is garbage. also two cards does run slightly cooler then one. my main problem with running the fans like that is it sounds like a jet engine in my face, while trying to listen to music or watch a movie or play a game. I am so pissed about this card. $280.00 trash!!!!!!          

any suggestions?????? besides spending more money.

You could try water cooling, aftermarket air cooling and/or improve case airflow.

I had the same problem...ran the manual fan settins i Catalyst to speed up the fan. Runs a little noisier but keeps the card cooler.