i've been trying to charge my n800 for the past day after it suddenly gave me a 'charge battery now' (red battery symbol) and shut off. it had been plugged in and on, running transmission and skype, for hours when this happened. it almost seems as if the file download was using more power than the charger was providing. the connector tip on my original nokia charger broke off, so i'm using a universal travel charger made for nokia. so, with the unit off (i removed the battery, let it sit for a few minutes, and replaced it) i plugged it in to recharge and the charging symbol would come on after a ~5 sec nokia white screen. but it then turned off completely. this happened a few times after unplugging and plugging it in, and then the charging symbol didn't come on at all after the nokia white screen. if i tried turning it on while plugged in, sometimes the blue led would come on, show the white screen, and turn off; and sometimes nothing would happen. i tried all sorts of button combinations and multiple power button pushes with no luck. it acted as if didn't have quite enough battery juice to start it's 'charging software' (if that makes sense. it doesn't really). and the charger didn't seem to supply the necessary power to start the charging either. i then plugged it into a usb charger using a cable purchased for this purpose. for a while i got similar results, then randomly the nokia white screen stayed on much longer than usual and the charging logo appeared.
it's possible that the replacement charger i got doesn't supply enough power to start charging a completely dead battery, but why would the battery be completely dead after having been plugged in and charging (the icon showed 'charging') for hours?
now i'm waiting for this thing, which i love and now hate at the same time, to get a full charge so i can re-flash the firmware and see if it turns on.
thanks everyone for all the info on this forum.