Don't know if this will do it for you, but every time I create/change any playlist information, I always delete all files and directories under the ..\program files\audio receiver\db directory(check the path as I'm typing it from memory....)

I was plauged by not finding tracks (new and updated ones) in the playlist and finding ones that no longer existed (missing ones) on my drive, even though it was rebuilding them when I restarted ARM. It seems to remember a previous scan of the entire disk which had imported Real Audio playlists and more, after that point they were never removed or checked again I guess cause I explicitly pathed the directories after that.

Anyway, it seemed to fix it for me. Good luck.
- Tim