my 7th gen ipod nano will no longer sync.

Using a windows 7 PC. In iTunes, the iPod comes up when connected + message saying 'ipod syncing' (although it doesn't transfer any songs to ipod). Can see the 2 playlists that I last loaded from iTunes to the iPod. However, when I try to manuallyforce a sync from iTune to iPod of either selected songs or entire library, get error message saying ;the ipod xxxx cannot be synced because it cannot be found';. Also error message 'disk cannot be found'. Tried several things: including: manual sync of ipod; drag & drop of songs from iTunes to iPod in tandem with 'scan for hardware; in device manager;reinstalling iTunes, restoring iPod (got error 1437). Any ideas?