My ipod won't sync any music, just started yesterday

I have a 4th gen ipod touch. At first the ipod would only sync a few songs that I got and now it won't sync any. I've restarted the computer to no avail. I also reset my ipod and and now it won't upload any music. When I click on the music section to manually select what I want to upload it never evens loads, I get the pinwheel. I tried to be patient and let it load but I waited 40 minutes and still a pinwheel. I then have to force quit itunes. I've unplugged my ipod during the process and I don't even get an error message. It is driving me nuts! My ipod now has no music on it and it seems I put on any.