I got a Sapphire 7850 OC edition with a stock of 920clock/1250memory. I overclocked it to 1050/1400. After the overclock, I started noticing that I would get some weird artifacts when playing game for about half a second. It doesn't happen often, but it annoys me. Additionally, when I surf the web, the internet would sometimes freeze for about minute, but I could still move my mouse around. Are these due to the high memory or clock?
sounds like your oc is unstable. most guides for ocing the video card, have you oc the gpu, test it. find a stable place. then reset it, and oc the memory, and find a stable place.
after you oced it, did you test with furmark, or uningine? that should get you pretty close to stable. I did oc my card once, had the tests run ok, then when i played a game it didnt like it.