I sorted it out minutes after making this post
Murphy's law...
Recently I moved some of my favorite music (which I play most often) to the HTPC from the network drive (so I don't have to keep it powered when listening to music)... the playlists had old reference (i.e. drive letter changed). I'd ofcourse, expect XLobby not to play 'em, but it's so "smart" not to even show playlists if songs in it don't exist!
Each day I learn something...
Cheers,
D.