iPod 2nd gen shuffle sync and ipod not found

I have a 2nd gen shuffle, I was able to load music on it. Now I want to change the music and am having trouble. I have iTunes 11.0.1. I see the ipod in the iTunes left hand pane and in the top window pane it says iPod sync is complete. Under settings I have the 'sync only checked song' checked. I want it to sync with a music file in my playlist. Under on this ipod, I have autofill from with the playlist selected. Under this in autofill settings, i have replace all items when autofilling. I select the autofill button and get a waiting for ipod. I've selected only 4 files and want the original files on the ipod replaced with the new ones. It does not appear to work. It says updating files, finishing snyc. After running for a long time, sometimes it says it's too full, sometimes it says can't find ipod. It always ends up failed. I don't have anything else connected. I've changed ipods, chargers and USB ports with the same result. Any ideas?