The i-Pod Cannot Be Synced

I have two i-Pod classics attached to my PC. Lately I've been deleting songs from my larger device (160 gb) and adding them to my smaller one (120gb). Suddenly I got this message on my screen and only for the larger Pod: 'The Gpm324's i-Pod (Name of Device) cannot Be Synced. A duplicate file name was specified.'

No issues at all with the 120, but no matter what I do, even when I delete songs, such as the two below, I get the duplicate file notice.

Anything I can do, short of restoring the i-Pod, to get songs downloaded into and deleted song titles permanently removed from it?

Thanks,

Greg