iPod 3rd gen iPod not showing up on computer

I have a third gen iPod classic, 40gb, which works fine until it gets plugged into a computer. It doesn't show up in iTunes, on the desktop, or in disk utility. I have tried this on multiple computers. The iPod shows an Apple logo, and then either turns off or asks me to select a language. Once I select a language, it shows the menu and displays an empty battery at the top of the screen. Other times, it doesn't prompt me to select a language and just turns off. If it does this, I can get it working again by charging it. How can I fix this?

Okay, I've figured out that it does sync via Firewire 400, but will still not sync over USB. Suggestions?

I know these iPods can't be charged via USB, but they can be synced with USB. They could only be charged with Firewire, but could be synced with either.

I think I get it now! I wasn't using the original USB cord that came with the iPod, I was using an iPhone one. Is that what I was doing wrong?