It’s possible that the song wasn’t in the mp3 format when you uploaded it. The Ning Network will give you an error message if you try to upload anything other than an mp3, but if you override the error message it will still try to upload it. If this happens, the music player will get “stuck” on this song. Try removing the song, converting it to the mp3 format, and uploading it again.
Songs may also display a spinning wheel if the song did not upload successfully or meet the requirements for being added to the network.
If you added a URL to a song file, make sure that the URL ends in .mp3. URLs that end in anything else won’t be accepted and won’t be able to play in your music player.