I bought my PC with 9800 gtx+ about a year ago and the seller gave me a low power supply of only 400 watt and told me that it'll be enough for my build, but after few months i started to notice that games get somehow buggy and the colors get all messed up just moments after i start any game.
it happens with all games and at the start it was barely a problem but now i cant even open high graphical games like farcry 2 or crysis.
the rest of your system? CPU, RAM, PSU?
Try your card on different computer and see whether the same problem exist, if yes then your card is broken...
Did u connect the 6pin power connector for your card?
About your PSU, what brand? model?
Could be your GPU is overheating. It could also be instability due to your PSU. If your system is a dual core and your PSU is a high quaility brand like FSP, Corsair, PC Power & Cooling, then it is more likely to be your GPU. If the PSU is some chepo brand, then it's more likey to be your PSU. Yes, an unstable PSU can begin to fry other parts of your system with spikes and drops in power, so your 9800+ GTX may be damaged.
my build is:
Intel Q6600 core 2 quad 2.4ghz
Intel G35 chipset
XFX 9800 GTX+
4GB Kingstone DDR2 RAM
the PSU (400 Watts) is some crappy brand that i dont even know what it is called, i returned the G.card to the retailer and he said that its broken and hes willing to compensate me with 100$, bc on the purchase he told me that the PSU would be enough, next time i'd be more careful since am new at building PC.
anyway its a good deal i suppose,
thanks for the help.