Literally just happened to me over the weekend. Was using my n900 as normal and plugged it in to charge and no joy. Windows wouldn't detect it either as a device, kept saying it was malfunctioning.

Back to the carphonewarehouse for repair and just got word from them today that they have sent it off to Nokia for repair under warranty. Its back to the n95 for me, weird using it again after getting used to the touchscreen and general speed of the n900.

long time lurker, first time poster btw!