Ipod classic won't sync properly?

I purchased a new iPod classic today. When I sync it, it adds most of my music, but towards the end of the syncing it comes up with "disk could not be read from or written to" and doesn't sync any of the music I've downloaded in the last few months. All of this music is downloaded from iTunes so should all be in a correct format.

I've updated all the software on ipod and my mac, I've reset the ipod, restored it and still nothing is working!

I bought the iPod because my old one was running out of space and now it won't put all my music on there anyway!! Right now it seems like a complete waste of money!!