problems when using 8800 Gts cards

I have burned through three 8800 GTS cards in the last 3/4 of a year to full year or so, and before i buy a new one (if I buy one) i wanted to know what the problem might be.

Specs:
850w power supply
Intel E6600 processor w/ liquid cooling system
Asus P5N-E SLI nForce 650i motherboard
Sony dvd drive
Hitachi 250GB hard drive

When i am viewing the desktop or anything in windowed mode, the screen flashes black for a second or two at first then goes back to displaying a picture, the longer the computer is kept on, the longer the black stays and the less the picture is displayed, eventually becoming so bad that reading anything becomes impossible. When i boot up Linux, i can leave the computer on for hours without this happening. I have searched google, but nothing has been helpful. Does anybody know what might be the problem? Your help is appreciated.

Did you overclock the card?

Hi

When you say you've gone through 3 8800 GTS cards in 8 months have you replaced your power supply since the first burn-out or continued using the same one? I ask as i burned out my 7800 GTX last year due to a power supply that misfired on one of the rails, blew the card but still worked fine afterwards, to the point that you'd never know there was a power supply problem.
Also, with your system being water cooled, are you 100% sure there isn't a leak somewhere? As stated above, if you've gone through 3 8800 GTS using the same components in your tower, then maybe it's time to check them over.

the card is not overclocked, and there hasn't been any moisture on the inside of the case, so i assume its not the cooling system. How long did it take for the card to go when you had the power supply failure?

How long to go? A split second, that's all - no blue screen or overheating prior to it blowing, PC just clicked off and i thought i'd tripped a switch on my electrical supply to my house. Tried turning back on and got a tiny burst of power, then it went dead. This happened every time i tried to turn on my PC, so once everything was checked over, it was obvious that it was the graphics card which had gone - i was playing HL2 at the time with res. set at 1600x1200, but had Nvidia temp control running and it hadn't overheated, just got a spike from powersupply.

my cards don't go right out like that but could the problem still be from the power supply?

What power supply u have?
Did you plug the extra power cord on ur motherboard?
(I know for example Qtech power supplys do some strange things when you do that)
And some motherboards dont need to plug the extra power cord,sometimes doing that u burn motherboard,cpu or graphic card.
And something different...is the power on ur house stable?

the side of the power supply says NZXT precise 850w, so im assuming precise is the model. I'm not sure where the extra power cord is supposed to be plugged in, but the power to the house is pretty stable from what I can tell.
thanks for all the replys by the way.

The main power cord ofcourse has the bigest plug.
The extra power cord is smaller and is usualy next to the main cord or next to cpu.
If its plugin remove it and try without it.
Note:before you unplug anything switch off the power.

I can't find any plug like that, theres only the plugs for the fans near the main plug and near the cpu