I've powered on my n900 (10 min) before charging it with my laptop usb port. The mic was ok. The next charge was in my car with my 6210Nav car charger and the little adapter from the n900. The mic is ok. Third time, i've used the n900 charger and after the battery was fully charged, no mic until i power off and restart the n900. Now i'll charge my n900 with all but the original charger without mic problem. Does anyone know the usb cabling diag ? I may try to see if there is something wrong with the voltage (with my fluke multimeter). Sorry for my bad english, i'm french.