Hi, this is a new problem, I was using my MacBook on battery this morning with no problem but this afternoon it won't work without it's ac adapter.

Without the adapter, when you turn on the laptop it begins to start as normal but then (within a second) goes dead, so I assume that the computer is getting power from somewhere, but not from the main battery. The battery test button shows that the battery has ample power left.

With the adapter, the laptop works as normal. It even registers the presence of the battery, charges it (it now reads 99% full), and gives no indication that there is any problem (in the about this mac bit it says that the condition is normal). If the adapter is then removed the laptop stays on for perhaps a second, then turns itself off, without seeming to do any shut down type functions.

Has anyone come across this problem before? I suspect a trip to the local apple repair extortioneers.