Yes, too aggressive an OC will cause errors in the science (that what this is all about after all) and foul the results of the WU. It will also push any shakey system over the edge. Just back off the OC a little and see if that clears things up.
Yesterday, I pushed my 1900+ XP a little to far and got mangled unusable WUs and my system started acting flaky. I've back it down one notch and now it is good to go.
