This is happening today and once yesterday. Every time I remove the AC plug or I'm on battery, my MacBook goes to sleep without me doing anything. It appears that my MacBook shows an X where the battery is. However, this is sporadic and it then reverts back to normal, but it'll repeat the cycle again. The only to resolve it is to plug in the AC. I have a March 2008 MacBook in which I bought it in June of 2008. I'm running Mac OS X Lion 10.7.1. What's going on?