Genuinely sad for your N900.

The USB ports have been known to fall out on the N900's as documented on this site. Users like myself have resorted to re-enforcing the USB port by soldering (or epoxy) down the USB port to board. It might be to late for your N900 now, but who knows? Maybe it can still be saved?

Refer to this thread:
http://talk.maemo.org/showthread.php...t=usb+port+fix

Good luck to you!