Oh, into a wall outlet. Got it.
Hmm... Maybe there's something about how you place the iPod when you plug it into the PC that isn't the case when you plug it into the wall. Maybe you've been putting it in an enclosed area, on top of something hot (the PC, the display), or in a room that's warmer than where the wall outlet is.
Some countries outside the US use higher voltages, so maybe this has something to do with that. Dunno. If the PC is sending out too much energy over the USB port, you might want get that looked at. Something like that would probably affect other devices as well.
Have you tried plugging the iPod into a different computer, or tried it with your PC plugged into a different outlet (especially an outlet that's on a different circuit in your home).
I'm no electrician or engineer, but maybe something in here will help. You could always get a powered USB hub.