I have the same problem!
brought a refurbished nano (4th gen) from apple and on the first hour of arrival, it froze. So I did the hold centre and menu buttons to reset and plugged it into the computer. I-tunes tells me its reseted and tells me to leave the nano connected until it shows up in i-tunes, but then comes back with the previous message telling me to go through the whole resetting process! im going round in circles!! HELP!!!!!!!!!!!!!