Problem with DX 10 and artifacts

So i just recently bought a 4890 for my system. at first i had windows xp and i overclocked my cards Core from 850 to 950. and the Memory clock tp 1175. (not sure what the stock is). Everything ran great and i got no artifacts or errors whatsoever. Now i installed windows 7. And i have a couple direct x 10 games, crysis and farcry 2. Almost immediatly i started getting artifacts, like clue squares showing up here and there. I moved the clocks down each by 50mhz. At first is seemed to work but after 15 misn of playing i slowly see more and more blue squares pop in and out. Is it possible that the overclock is stable in dx9 but not in dx 10? im sure exactly how it works.

i clocked it down to 900mhz and everything has been fine so far. i think the dx10 effects was enought to make it artifact at that clock speed.

it is artifacts, but they're minor. dx10 probably stresses the GPU more than the dx9 in those games. crysis is a game that is very problematic w/ overclocks, i use a special profile w/ it.