I just got a MacBook yesterday (2.0), and clamshell mode *was* working yesterday when I played a little WoW, but now I'm having a bit of a problem. I have an external 20" connected to the MacBook. When I close the lid, the MB goes to sleep as expected. But when I wake it to again to have it run only on the external 20" (as I was yesterday), it goes right back to sleep by itself after a few seconds. Wake it up again—back it goes four or five seconds later. Sometimes it will go back to sleep instantly. The external has a menu and IS the main screen while this is happening. Any ideas, people? Hopefully it's something simple I've just missed in the prefs, but I don't see anything. Thank you!