iPod Touch will charge from computer USB, but not from AC outlet I have an iPod Touch.  If I plug it into the AC outlet, with a AC/USB power adapter, the iPod will charge to about 20%, and then stop charging.  However, if I plug it into a computer USB outlet (using the same USB cable), it will charge fully to 100%.  

Electricity is electricity, no matter where it comes from, so why wouldn't it charge from an AC outlet?
It sounds to me like your AC to USB charger is having a problem with heat.

It charges for a while (while heating up) then it stops.

If you let it cool down for a while I assume it continues charging.

In any case, I would suggest replacing it.