Looking into the usb port problem, after taking the N900 apart it is very clear to see that because of bad design the usb port fixing on the m/b is so bad a design fault on the N900 it is destined to break off, this means only a re-design will put it right.
A temp repair is possible but will invalidate warranty if not done by Nokia so it appears.
Where does that leave us ? after looking at the thread regarding the usb problem it seems many people are having problems with Nokia regarding this.