Playlists won't synchronize

I have an iMac, Macbook and iPhone on the same iTunes Match account.

At some point in the past, they all synched up and matched playlists.

Now - when I remove playlists I don't want any longer, they come back. Doesn't matter which machine I do it from, and I've done an Update Itunes Match in my iTunes library after doing it .. it still comes back.

How do I force playlists to stay synch'd?