Unable to initialize iPod

I recently bought a 30GB colour iPod over eBay. I initialized it right away, then imported all my music onto it. It worked perfectly for about three days, and then it wouldn't play songs - it would just skip and maybe play every third song. The next morning, after I plugged it in to my brother's laptop, it wasn't recognized and all the preferences and songs seem to have been erased. I've tried restarting it several times and it never saves any of the preferences. When I plug it in, it doesn't appear on the desktop or in iTunes. However, after five minutes an error message appears and tells me that my computer can't read the volumes on the disk and asks me if I want to initialize it. When I try to initialize it, disk utility freezes while trying to partition the disk. I've tried plugging it in using both USB and Firewire into both my iMac G4 and my brother's Powerbook without any change in the condition. Does anyone know what I should do? I assume it's a hardware problem, but I want to be sure before I send it in.

-Nick Sweet