The power supply is a Thermaltake 850 Tough Power.
It has four connectors that are black and four connectors that are red which attach the cables to the supply. Would it be better to connect each graphics card power connector to a different color connector on the supply?
As suggested try installing ATI 10.4 drivers, I have found issues with the latest drivers myself and have stuck with 10.4 for performance reasons. You may want to test the memory and verify that it isn't another issue instead of the 5850.
i have same problem people say it could be anything from psu to drivers and possible the idle clock shift idk forsure but im about to try over clocking it just a bit to stop it from idling to see if that stops it
The problem was software drivers and compatibility. I'm still picking my way through it. Watch out for Steam, that thing is a head ache. I think this would have all been easier in XP but then no Directx11. Check you video card control panel for configurations.