Thanks for the post Andre. I'm syncing via the Windows Media Player on my PC, which used to work fine. Now, however, all the music comes over but no playlists ie in the Playlist category in Power Amp there is nothing.
I'm beginning to think the problem is in the sync between the Media Player and the phone and it is this behaviour which has changed. My music collection on the PC is fragmented and disorganised (eg some Kraftwerk albums are in a Kraftwerk folder, others are in a Krautrock folder), though I have organised it via the Media Player library. When I look at how the music is dumped on the phone, it is all reorganised much more logically (ie all Kraftwerk albums in a Kraftwerk folder). This is great, except that the pathways contained in the playlists are no longer valid for all tracks. Maybe that's why the playlists won't sync or have been stopped from syncing any more.
All I can do is fill in the blanks on the phone, though it would be good to back them up once done. presumably the export option allows that.