Things you can try:
- Other USB port on the PC
- Other cable
- Other PC
- Other iPod on your PC (just for a test, don't synchronize!)

If it's clear that it's an issue with your iPod, I'd post in the http://forums.cnet.com/mac-forums/iphones-and-ipods-forum/ for specialised help. Maybe it needs to be resetted or something like that, but I'm not the one to suggest such.

Kees