After upgrading to beta 13, his XML pages still worked fine for me including the playlists.

Since upgrading to beta 13 requires that you re-install his files from scratch, I would bet that the problem was caused during your re-upload. Perhaps some of the files didn't get sent, the directory structure wasn't properly replicated, the file permissions didn't get set correctly for all of the files, or you forgot to set it back to read-only before rebooting, causing file corruption.