Why does my iPod say it has synced but doesnt sync any new songs and stays on the do not disconnect screen after syncing?

Hi, I have a 3rd gen iPod nano. When i sync it to itunes using the original adapter, it syncs automatically and says it has done it but then after instead of just proceeding to the menu on the ipod it stays on the do not disconnect, eject before removing, connected screen. It will stay like this forever unless i manually eject it but then when i do this it hasnt synced any of the new songs ive added to itunes. I dont understand y its suddenly doing this!

Can anyone help me PLZ!?