Good evening from Albuquerque,
I only assign ratings from within MC18 - I build playlists for all of my songs that from within MC18 I have assigned a 5 star rating, and when I sync I only migrate over the 5 star songs (and their associated playlists).
Before I shuffled around my drive letter assignments, the iPod wouldn't show up in MC18/MC19 - I could easily see it from within iTunes or Mediamonkey.
HTH,
Scott