The playlists show up in explorer as 0byte files, and they aren't read by Google Play Music, WinAmp, RocketPlayer, etc. I believe that they're actually 0 byte files.
I have the same problem - on device Creative ZEN, MB V3.2.6827.
Playlists synced by MB are on the right and all show as zero length (here in Beyond Compare, but also in Explorer), whereas the same playlists synced by another program on the left show as their real sizes.

The playlists do play on the device, are readable in another Windows music program, and do show content in Explorer:

but a copy to hard drive mode by Explorer (and all other programs I've tried, e.g. Beyond Compare) shows empty:

The workaround of using a different playlist format isn't available on this device.