Hi I just recovered a N900 with broken usb to reliable charging.

1) Took it apart (easy peasy)
2) Pulled off the sd card module and taped it to the back (why is that glued anyway?)
3) Took some cotton swabs for insulation and taped around the usb port so hot air gun wouldn't fry other components.
4) Blasted the micro usb port with 450c hot air gun with fine nozzle, while clamped with pressure.
5) Kneaded a bit of epoxy putty around the cleaned sides of the usb port, with a cable inserted to avoid gunking up the inside.
6) After hardening, Used a dremel to grind away the blobs of expoxy that interfered with keyboard and case fit.

Now i have reliable charging, but unfortunately no USB-data. Better than nothing, and it was easy.