Ipod touch WON'T charger, but WILL sync

This has been going on for a while-
I plug the ipod touch into my macbook pro with the cable it came with, and it comes up in Itunes, just like it should. Sometimes it charges, most of the time it doesn't.
9 times out of 10- I plug it in and the charge comes up fine, then a minute later the charge sign goes away and drains the heck out of the ipod.
By this I mean the icon and everything comes up in itunes with the battery display next to it. But when it's charging it has that little "lightning" symbol in the batter. Instead i just get the batter with the amount charge left shaded in. And when it does this, the batter drains down incredibly fast. I mean about 1% ever minute.

please help, I take this thing everywhere!
-Jmurr

The next time it does that, select "eject" but instead leave it connected. Let's see if it starts charging correctly. It almost sounds like it might be overloading your USB port. That might indicate a defective battery.

Let us know.

Regards.