iPod will only charge with computer - not with any other device

I've owned my iPod for a few years with no problems at all. I started experiencing this problem suddenly with no cause. My problem is it will not charge with any other device other than connecting to my computer via USB. I have 2 docking stations, a wall power adapter, and a car charger, and now none of those will charge the iPod. They will still play the iPod, but will not charge. My iPod nano works fine with all of these other things, so I know it is not the docking stations or power adapters themselves. Other than that, the iPod seems to work fine. My guess is this is not a battery problem, but rather a mainboard problem in the iPod. Any ideas?
Thanks