is this possible???

i have a GTX 260 Core 216 and i oc'ed it to match the GTX 260 (192) FTW edition and i used a program to watch for artifacts called "video card stability test" and i ran both modes, it has a artifact watch mode and a benchmark mode. i used the artifact mode for 3 min with none then i let the gpu cool down for about 5 minutes then i ran benchmark mode which runs for 3 minutes and rates your fps. so i get no artifacting on either modes in this program and then i play gears of war and on one map (canals) i noticed on a wall there were black lines like tearing up and down it, ill try and get a pic of it after dinner (getting cold) and when i moved the camera they like flashed. its hard for me to explain but if anyone knows what this sounds like and could confirm what it is its greatly appreciated. oh and my temps never go above 61C using either the stability test or the game with a 45% fan. i have my temp and fps displayed in the top left corner of my screen when playing games using evga precision overclocking tool.

Try lowering the OC by 5-10mhz at a time.

ozone3d furmark

type those two things in google, you should get a gpu stress test... put everything on high, and just let it run for a few hours, than come back to see if you see white/yellow dots popping up and around