M17x R1, System is operating on battery power, AC is connected?

Hello there,

When I turn on my M17x R1, I get two loud beeps and the following error message:

System is operating on battery power. To maximize battery life, the system will operate on integrated graphics. If you would like to use discrete graphics, connect the AC adapter. Press to resume, to Setup

The problem is: the AC Adapter is plugged in. What is wrong with my system? I need this to be fixed fast, since this problem is annoying as !