Miscoloured pixels

My card stays pretty cool, I've never seen it above 50 Celcius
You mentioned voltage, would a larger power supply possibly remove the problem?
EDIT: Also my video card is factory overclocked, I have done no overclocking to this computer myself. If it's an instability problem at those frequencies do you think it'll be a warranty replacement?

How would I go about downclocking it? Would I use nTune? That sounds like it may affect my warranty, I know I'm going down not up, but still - I'd rather not, if it can't handle the clock speed they sold it as I should be able to get a replacement.

Personally, I would use CoolBits. It is a simple and effective way. All you need is to create a DWORD in your registry and reboot. This will unlock Advanced settings in your driver control panel and will allow you to set your core and memory clocks to whatever values you wish.

I agree that you should write down current clock settings and downclock them to reference card defaults. This will not void your warranty. If the problem goes away you can then begin overclocking in small increments (like 5 MHz at a time), rebooting and running games or 3DMark05 / 06 until you see the problem return. Then go down about 5-10MHz on both GPU and memory clocks. This way you will have the highest OC which does not cause problems.

EDIT: I realize that you bought a factory OCed card because you wanted the meanest beast possible. But in truth, the card is plenty fast without OC. So don't feel bad if you have to downclock a bit.

EDIT2: I would start with downclocking the memory, actually. 1.75GHz? Wow, sounds a bit much.

Unfortunately a bigger or better PSU will probably not help unless yours is really crappy or dying. As far as the temps concerned it does not matter if you see 50C. Check to see that your heatsink is firmly attached on your GPU, if in great doubt, remove it altogether, apply some paste where and if needed and reattach. If your problems still persist just take it back and ask for another card, or downclock it and leave it there, or do a GPU voltage mod. But that last option is really only for those who are technicaly educated and really KNOW what they are doing. If you fry your card by voltmodding, forget all the warranties and goodies.

In short:
1) Check the heatsink on the card
2) If its ok just take the thing back and get another one

Good luck my friend