I had what I suspect is the same problem while teaching my mother to use jemplode on their central this weekend. Created a playlist, put some things in it, went down to play it and it wasn't there. (Well, it was available for editing on the central, but didn't even show up after edited) I reconnected with jemplode and it told me it reattached an unattached playlist, so I resynced and everything worked fine. We created a few more playlists that worked fine the first time.

I was going to write this off as wierd central bug, but perhaps it's not so isolated.

Matthew