The later nano may require more power when connected, to operate and charge its battery, compared to the older nano. It's possible that your computer's USB bus may not provide sufficient power, if you have other devices connected at the same time.
As a test, I would shut down (power off) the computer and disconnect all USB devices (including hub), except for standard keyboard and mouse if normally used. Do this to Reset the iPod
Start up the computer, run iTunes, and connect the iPod to a direct USB port on the computer. Is there any difference regarding this problem?