I'm having the same problem, except that I can only see ONE song title in the left pane.
My setup is on Linux, Fedora 16 (was running 15, with same issue, if that matters). The actual music resides on a network share, which is a Windows machine, and I have SMB/Cifs configured to mount the music folder into /media/music - and this works with no problems.
The one file that does show up on the left is in the "root" of the "music" folder. Everything else is in a folder or subfolder.
I have tried clearing Subsonic cache files, browser cache files, a different computer, a different browser, a different user, none of which have worked.
Finally (just now actually) went to Settings / Media Folders, and disabled my music folder, then saved. Subsonic reported that it couldn't find any music folders. Went back and enabled the folder again and saved. This seems to have fixed the problem.