problem with 80 gb ipod classic not syncing?

The problem I'm having is that whenever I connect my ipod to itunes it will sync only about 2 gb . Then when you disconnect the ipod there isn't any music on it. My songs aren't corrupted or anything, I had an old 80 gb ipod that worked just fine with them. My sister even tried to use her itunes with the ipod and she's getting the same error. I've tried restoring the ipod to its original settings, I've formatted the ipod, and i've used disk error check on it, I updated the ipods software to the latest one, I have the current itunes. Any suggestions would be greatly appreciated. I have windows xp by the way and my sister has vista. So if your help only pertains to either one its all good.