Of late I've been getting the message that the USB Device is not recognized repeatedly. shortly thereafter my battery dead. In fact I've learned that I ought to shut down immediately after seeing that message. Has anyone else seen this problem? It's becoming a near daily experience and whatever it is it's definitely hitting the battery.

N800 2008 OS ~1year old. Original battery.

Do you see that without anything connected to USB port?

Maybe the USB port is stuck in host mode... If so, the +5V USB power regulator keeps running and likely shorten the battery life. Maybe you can try to reset the USB to OTG mode? (For instructions see the wiki page.)

nothing connected.

Maybe the pins 4 an 5 are shorted together in the N800 connector. This would force the N800 into host mode and would cause the error message you are seeing. Maybe try checking the port with magnifying glass if you can find any foreign object or bent pins?

If you don't find anything there may be hardware failure inside N800. Maybe a last resort before sending the N800 out for repair is to try to reflash the OS?