Well, you can try using a different cable, a different firewire port, or a different computer (sounds like you may have done this, but it wasn't clear). If it only happens with your computer and not someone else's, there could be something wrong with your software, your hardware (like the firewire port) or one of your songs could be corrupted. If it happens on someone else's computer too, then the problem may be with the iPod.
You could also try making another user in OS X (assuming you are on a Mac), and making an iTunes library with just one song to test if it will sync.