The yellow light will go off when you unlock the device. This is a normal feature. Doesn't mean it isn't charging.

If the battery in the clock box isn't animated and moving then it might not be charging.

guys reflash ur phones . . . . . this bug will be fixed in the new firmware update . . . if u notice . . when there are too many heavy apps running the n900 this problem occurs . . . jus give the n900 some flashing . . . . it will be good to go. . .

I've noticed this error message a couple of times as well. But in my case, I keep the N900 topped off when I'm out and about via a 12V @1A DC charger (a car cigarette lighter charger). The N900 specs call for a 1.2A (1200ma @ 5V current). It charges fine so long as the battery is not *too* low. When the battery is low, the charger doesn't supply enough juice to satisfy the N900's charging driver, and it pops up the "Not Charging" message after a few seconds of it being plugged in.



Why it's doing it when using it with the supplied AC charger as in the OP's post...? ~shrugs~
In my case, the AC charger seems to be able to keep up with the phone (yes, yes, "It's not a phone!"), and charges it just fine.

is it possible that the battery is somehow broken and telling its full already or is it a software issue?

In my case at least the problem was the charger!!I got a new one from Nokia, and this one charges the battery with no problem at all so far.Therefore,try a different charger and see if that helps!The one i have that is not original from Nokia doesn,t work as well(only charges when the phone is off).

The charger that comes with the N900 is marketed as a "smart charger" -> does this mean Brussels law has limited the output power for global warming reasons?
Check the output of the charger(written on the charger) versus other nokia chargers..

Im using the original nokia charger so i think mine is a different problem. Also happens when charging with usb. Not charging.