I recently got a MBP 2.33 Ghz and have been extremely happy with its performance. Have been using my MBP since morning today and it was fully charged and was plugged in. So after about 10 hours of using it, I decided to plug it off and run it on the battery. It just shuts off instantly when I plug out the AC adapter. Repeated tries to switch it on wont help. It never starts up. But if I plug in the AC adapter, it starts up fine and shows 100% charged. Also the iStat pro widget indicates the battery health as 79%. It was 97% in the morning. Any suggestions as to what is happening ?