Gnome Power Manager is in Batery mode when it is on AC

MSI PR200 laptop with Ubuntu 7.10.
From time to time, power manager indicate "power on Battery" when it is on AC. After few minutes it returns to indicate AC, and so on.
I had to modify the Preferences not to reduce the Display brightness to be able work without brightness flicks.
Power Manager not always is able to indicate the level of Battery charging.
All the above is not major problem but more nuisance.
As the problem is intermittent I'm not sure it is the signaling from the laptop or the OS/Gnome itself.