Artifacts after gpu oc

[Ticonderoga]

I have been running my HD7950 just above the 1 ghz mark for a while now and yesterday I noticed some artifacts in BF3 (black lines comming out of peole).
I quit the game, rebooted and ran of couple of loops in Unigine Heave = no artifacts?
So is it because my card cannot go any further or does it simply need more voltage to be stable? And are the artifacts caused by the oc on the core or on the mem?
ASIC is 89.1% on this card.

Cheers

 

[Ticonderoga]

Thanks, I will try lowering the mem oc. It seems like a have a strong core, I can easily go up to 1100-1150 mhz on the core but the mem won't go past 1450 mhz (at least not stable anyway)

 

[Ticonderoga]

The artifacts that caused by core clock overclocked too high are usually numerious (green) dots appear on the screen, where as "tearings" (which looks like lines coming out of things) are usually caused memory clock overclocked too high.

Then it is def. the memory, too bad my memory won't go very high. Hope it won't affect the performance too much.
I also had my screen go grey and lock up, but that seemed like a core issue.