What program did you use to import them back?
Usually I use Senuti.
If you did follow along, I'm not sure if you could do it in other programs.
Create the name of the playlists you want to copy, in iTunes.
Open Senuti (or other app) and find that playlist in iTunes.
Find the playlists on your iPod, select all songs and drag into iTunes playlist.
That should work, but I'm not 100% positive.