Ipod not charging when connected

Hi,

I have an Ipod 160GB.

Whenever I connect my ipod to PC, it's not charging and my itunes doesn't show up. I have already enabled the "Open itunes when ipod connected" option.

Only when I reset the ipod while connected to the PC and itunes opened, then it starts charging and synching.

My 80GB ipod doesn't give me this problem at all.

Thanks in advance.