Yea, looks like ur at the edge. Most LE's don't go past 190/190. Be carefull tho. Some people report that when near the limits of the card, performace actually decreases. For example, my friend's LE will do 55fps at 180/180, but go down to 51 fps at 185/185, even tho there wasn't any noticable artifacts.
So do some testing so see if u are losing performace by oc'ing the card too much. Dunno why this happens, I've only seen this happen to Radeons.