http://us.battle.net/wow/en/forum/topic/12504571125 for example. You may need to pull back the settings until it's OK. As to it used to work, all it would take to blow up is a Game/VideoDriver/OS/other update. Then you are back on the bench saying "What happened?"

There is that issue with GPU heatsink compounds that those that say "temp is OK" will not go fix. It's all over the web now.
Bob