Problem:
I've had this card for about 2.5 years, and it runs smoothly most of the time.

Last week I got the Diablo 3 Beta key, and installed the game. Once I logged into the game and started playing, one of these will happen after a short while (I've never managed to walk into New Tristram from the initial spawn point).

(1) The graphics on the screen freeze, the keyboard and mouse may be responding for a few second and then dead, the sound may continue play for a few second and then freezes. I have to do a hard reboot in this case. This usually happens when I play the game in full screen mode.
 
(2) The screen turns completely grey, or green, or some other color, the keyboard and mouse stop responding, the sound may continue play for a few second and then freezes. I have to do a hard reboot in this case. This usually happens when I play the game in windowed mode.
 
(3) A dialog pops up saying the graphics driver has stopped responding and has recovered. Game crashed but the system stays alive.

At first I thought it was D3 Beta's fault, so I tested with other games and applications. 

For Modern Warfare 2, which run smoothly without problem before, (1) and (3) may happen at random time, (2) never happens. I also encountered (2)(rarely) and (3)(more often) when playing Minecraft.
 
For other games I've tested, such as Red Alert 3 and Starcraft 2, they all run smoothly. I also run 3DMark Vantage several times, no problems during the tests.

The temp on my graphic card seems to be normal, 40~50 idle, 60~70+ under load.

Lower the graphics settings in the games does not solve the problem.

I tried different version of the driver, from 260.99 to 285.62 to 295.51Beta, none of them solve the problem.

I also tried removing the OC I've done to the CPU and memory, that does not help either.


System Specs:

EVGA X58 3X SLI MOBO
Intel I7 920 OCed to 3.36GHz
Corsair Dominator 3 x 2 GB 1600MHz DDR3 Memory
EVGA GTX 295 CO-OP
Cooler Master Real Power Pro 1250W PSU
Win7 64 bit OS

What happens if you run EVGA Overclock Scanner for 30 minutes?

It seems to work pretty well without any problems. GPU 2 heat up to 75 degrees, GPU 1 does not seem to get tested.

Install the latest drivers and use the option for a clean install and see if the same problems occur. Monitor the heat while the GPUs are under stress.

Clean install the drivers (260.99 and 285.62) does not help. Before the freeze happens, the load and the temperature on the GPUs are normal (60~70 degrees).