Hey there. I bought this Palit GTX 260 Sonic card about a half year ago, and ever since i've had this weird problem. Let me tell you something about it.
About once or twice a week when i'm playing a random game, the screen goes black and after a few seconds it restores back to normal, but after that my FPS goes very low. It's as if it went into a safe mode, but it doesn't. I've got a 500w Antec Earthwatts, Q9550 @ 3,63ghz, 3gb ddr2 800mhz corsair and a P5QL-Pro. Oh, and my OS is Windows 7.
I've tried to change every game's settings to low and forth, but it doesn't help. I have my graphic card drivers up-to-date and it is not overclocked from the defaults. The only way to restore the FPS in games back to normal is to restart the computer. So far i haven't found out any other way. All temperatures are fine.
Here's a fine example about this moment of horror:
I'm playing Batman Arkham Asylum. I've played it for almost two hours now, and my GPU temperatures look fine as they're around 60. A cool cutscene shows up and as i'm watching at it with an FPS of 100+, my screen goes black for 3 seconds and then restores back to normal. However, after this black screen my FPS is a horrible 30. Now the only way to make the game playable again is to restart my computer. As i said earlier it happens once or twice a week. At first i didn't think it was much of a trouble, but now it's starting to piss me off. I've tried to Google, yes, but without any solutions.
Nevermind. I think i found the solution by googling "3D and 2D clocks graphic card"... I found out my GTX 260 was changing between 3D and 2D clocks in the middle of gaming, and as you know 2D clocks can't handle games well I just overclocked the 2D to the same as my 3D were and now it doesn't really matter if it changes it. Thanks anyway