GPU , heatgun , GPU re-balling, 3RLOD , cooling mods.
start searching. you'll find a lot of people with the same problem.
if you're experiencing graphics problems , more than likely you'll start gettig the 3 Red lights soon.
there are a few different methods people have used with varying degrees of success.
you should try to keep it cool as possible and maybe do a fan mod.it might buy you some time.
other than that , I'd just keep using it 'til its completely dead and then try the heat gun mothod.
unless you're still under warranty, in which case, don't touch it. just send it back to MS and get another one.
or even better , bring it back to where you bought it and try to get a brand new one(if you send it to MS you'll probably get back a re-furb)