Hmm lately my NZ90 has had a problem charging. I pop it in the cradle and some times the charge light doesn't come on. What's odd is I can do a hot sync and the charge icon looks right but the charge light doesn't come on and the battery doesn't seem to be charging.
It I wriggle it, I can usually get the orange charge light on. I do use a belkin USB charge / sync cable and I wonder if I didn't break the port - which is Sony's reason for telling people not use 3rd party cable on the NZ.
Still, I blame Sony for making sure an inaccessible port.