MacBook turns off when power cord is removed.

[smarieee]

The title basically sums it up. The computer turns off right when the power cord is removed. It started earlier today. Never had the problem before.
I don't know if this would affect it, but my husband installed Firefox 3.0 a few days ago... anyone know?

 

[Counterfit]

Well, first, reseat the battery, and then try again. There should be a small button on it as well, and when you push it, all, or all but one of the nearby LEDs should light up.
Are you still under warranty? If you are, Apple might replace the battery, because that's not really a symptom of normal wear and tear.

 

[gusious]

Probably something with the battery.

Click on the Apple on the menu bar and then on About this Mac/More info and then check on "Hardware" the "Power" tab.