Few things are as frustrating as the music app on your iPhone or iPad not working properly. Below is a possible fix.
If you are using iOS 5 Beta 6 or 7, your iTunes purchases no longer play:
Connect your device to iTunes;
Under the music tab, go to the section labeled "manually entered";
Remove those songs, & re-sync. If you sync your 'purchased' playlist, they should stay on your device.
Did this work for you? Leave a comment below.