I have 2 EVGA GTX 590's that are used with a 6 monitor setup for Flight Simulator X. Everything has been running perfect for a year and a half. One day last week when I tried to run the game, the monitors would flicker and it would kick back to the desktop as the game began. I've tried everything possible to fix it (patches, settings, etc.) to fix it, but to no avail. I decided to try some other games that worked before (Battlefield 3 and Supereme Commander 2) and both developed the same problem. The game starts and immediately crashes to desktop.
As a last ditch effort I decided to reformat the computer. Reinstalled Windows 7 x64 and agot ll of the drivers loaded and..... SAME problem! So I thought it was a hardware issue. I took both cards out and put them in one at a time. With each card installed individually (3 monitors connected) the games worked like the should. Both cards separated had no problems. However when I put them both in together it crashes again. The windows background and icons appear on all 6 monitors as they should, but wont work when I start ANY game. I did discover when I plug in up to 4 monitors (in any order in any port) it continues to work properly. As soon as I plug a 5th monitor in games crash. It doesnt matter what monitor or to what port or what game. Temperatures are fine and the desktop memory tested ok. I've talked to other computer techs who are baffled. Any ideas? Please help
Power supplies do lose power slowly after a while.
You may have had it long enough that it just can't support all that you want it to any longer.
Just a guess.