Can't mine any non-scrypt coins

[UltraJake]

So recently I tried switching back from mining LTC to BTC for a change, but when I did this cgminer presented me with nothing but a series of "GPU0: invalid nonce - HW error."
Googling this has me worried that I have fried my card or something, but here is the catch: I can mine LTC without any differences in speed or general performance and I can play games using my card (XFX 6950 2GB) and I will get the same FPS as what I would expect.
Why would this happen? Is there a fix? Is my card still fried? (And if it is, would XFX cover it? I do have a Double Lifetime Warranty, but I'm not sure if I am still covered since I did some minor overclocking.)

[UltraJake]

Bump. I'd ask the dedicated support section, but I asked to get out of here days ago and nothing was ever done. 

[phrozenspite]

which mining software and pools are you using.  That might be helpful for us to know

[UltraJake]

Ah, of course. I am using CGMiner 2.11.3 and I have tried switching between BTCGuild, Coinotron and Eligius.