weird graphics corruption when overclocked on 8800gs

Hi all. Recently I got an evga 8800gs for my rig http://www.newegg.com/Product/Prod [...] 6814130332 , and while it runs fine at stock, once I overclock the core to around 670 mhz from 550 stock, some of my games get massive graphics corruption within 20 seconds of starting. The game will freeze for around 10-20 seconds while sound will stutter and then play again, but eventually I can alt+tab out or ctrl+alt+del out. And by massive, I mean the whole screen goes haywire, random colors flashing, textures whacked out. The thing is, I don't even get artifacts when testing with ATItool for 3 minutes until 700 mhz, so I don't know if there's something else that's wrong with the card, or if it's normal for an OC. So, if anyone knows if it's a driver, hardware, temperature, game programming, or whatever sort of issue, or if that's simply the limits of the GPU, I'd appreciate their input. I just don't expect that raising the gpu core a few mhz would go from working perfectly fine to massive failure, as I'd think artifacts would show up first. Also, the temperature on my card max's out at 65*C when gaming, current gpu clock is 663.43/1728/1053 according to rivatuner hardware monitor.

System specs:
Intel e2160 @ 2.8 Ghz
ddr800 ram, running @ 624 4-4-4-12
ga-p35-ds3l mobo
550w psu dual rail 18a on each +12v
win xp sp2 32-bit
evga 8800gs

Ok, thanks for the reply.

Not really. 8800gs is supposed to be like that.

I remember the old 7900gt cards that came factory overclocked had issues like this.

Bottom line, yes this is normal results for a card that is too overclocked. It's usually the ram having errors, as a result you get corruption and artifacts, locksups and usually completely reboots.

Return clock to normal and hope nothing is permanently damaged.