I must agree again - I had a heavily overclocked 8800GTS - that was a REAL TROOPER - ran like a demon for almost 2 years (and I mean almost 60% overclocked) before it developed this problem.
I then Baked it at 210c for 10 minutes - and it worked just fine again!
So I overclocked it again... and it broke again... So I baked it AGAIN!
And blow me down if that didn't fix it a SECOND time! XD
Anyway it sounds crazy - but yeah baking them in an oven actually COULD fix that error on those cards - but find and read a GOOD tutorial on exactly how - if you do it wrong you can totally destroy the card - and give it a LONG LONG LONG time to cool down - many people just opened the oven door and whipped it out as the timer was done and the card warped horribly (and obviously destroyed itself) from the different components cooling at different speeds. (Yes I KNOW this didn't happen to everyone but lets all realize that the average ambient room temperature varies GREATLY around the world and not everyone lives in the same country
Once you have finished your bake - just turn the oven off - crack the oven door open a little bit and let it cool down nice and slowly.
Also if you have changed the STOCK cooling system - do some extra research - I believe part of how this method worked was something to do with the stock cooler pressing the chips onto the board and the heat re-soldering the contacts under the chips - one would remove all the PLASTIC from the card - but leave the metalwork of the cooler in place.
I heard of a guy who baked his with the metalwork removed, and his chips fell off the board when the solder melted - obviously this is a non-recoverable fault.
EDIT : xBruce88x : Yeah - I got here just before your post - but yep - that's why the tutorials I read said that if you have the stock factory cooler rather leave the actual heat sink ON and just remove all the plastic work, as the actual heat sink acts like a vice holding all the chips in place - And oddly enough all that heat seemed to improve my thermal bonds as the card actually ran 8c cooler on average after the first bake