iTunes wont sync some playlist content to iPhone 3GS

I got a new MacMini to replace and old Powerbook. I moved the library over, ran iTunes which updated it. It didnt require me to reeastablish the iphone/itunes link. I thought everything was good for a while.

I created a new playlist and set it to sync. It syncs the list name, but not the songs. Removed the playlist, synced, re-added with a different name, synced, same outcome.

Wiped out iTunes library on Mini, then it made me reestablish the iphone/itunes link, then synced, it removed all songs and playlists from iPhone as expected. Added all songs back to iTunes library and rebuilt newly named playlists. synced. All playlist names synced, but still i have two that wont sync the actual songs.

The playlists show songs in iTunes. Both are smart playlists which are set to sync one or two genres each. The lists that work are also smart lists.

How can I fix this?

My thoughts (please advise if it sounds right):
1) Restore iPhone to factory.
2) Wipe out iTunes library on Mini.
3) Import my songs to iTunes and recreate the playlists.
4) Setup iphone/itunes link and sync.