This sounds like a different problem. I believe most of the people with random shut offs do not see a difference whether on battery or AC. I think you have a bad battery.jrichter said:This also happened to me after doing the OS X update.. Drives me crazy as it just shuts off unless my laptop is plugged into AC! ... the battery always shows a full charge! ... This never happened while running 10.4.6. I have a very early MacBook Pro CoreDuo 2 GHz system.