I am also having the same problem, have the playlist folder set to
D:\My Documents\My Music
where my playlist are stored in .m3u, and work on mediamonkey on local computer
when I try to access them via subsonic more actions ->Load->Load it displays a empty playlist.
Any help is appreciated
EDIT: Just found the solution elsewhere http://forum.subsonic.org/forum/viewtopic.php?t=1808
seems to be a problem with absolute path