Ipod sync issues

My iPod Nano, which is around two years old, shows up in iTunes but isn't being recognized by my Mac computer. It's not syncing properly there are songs missing on my iPod which are on my playlist on the mac. I am using iTunes 10, Mac OS X version 10.6.8

Are you sure that the cable is in working order? also check to see if the iPod is in Macintosh format so it can be read on the mac.

Yes and Yes.

The cable has always worked before. We got it in Mac format two years ago and we haven't changed it since. Has anybody got any more ideas or suggestions?