Comment 12 for bug 558627

Same thing for me with a Dell inspiron 1010 (aka mini 10)

In my case the problem is the netbook, not gnome-power-manager.
But because its a common problem. gnome-power-manager seems to be the right place to put a workaround.

If I watch /proc/acpi/battery/BAT1/state I can see that inmediatly after unpluging the power cord, the "present rate" climbs up to 76000 mW. After 4 to 6 seconds drops to 900 and 4 seconds after that starts stabilizing.

The real rate is about 11000 mW.

After unpluging, no matter the remaining capacity, the very high discharging rate reported leads to miscalculation about the remaining time. Very little remaining time, and the netbook hibernates.

One workaround possible is to wait 10 or 20 seconds after any "charging state:" status change before taking any other measure that can lead to an action.
Other workaround can be to ignore the state when it reports a ridiculous out of scale value. In my case I cannot make my netbook use more than 13000 mW, so 75000 is definitivly a bad measured rate.