First, make sure that you have the right path to the mt-daapd.playlist in your config file. The config term is “playlist”.
You can check to see if your playlist is recognized by running mt-daapd -p. (You might need to do -p -y). This will parse and display the playlists on the screen, so you can verify they are correct.
Probably there is a problem with one (or more) of the playlists and thats making the playlist compilation fail.
In any event, playlists work great with the SoundBridge. I use them all the time, so there is definitely something going on with yours. Probably it’s simple — a typo in the config, or a typo in the playlists or something.
So start with the -p, and see where that takes you.