I had this too, it would say preparing to update and the song would be greyed out, now if i try it it would delete every song on my phone and seemingly I can only have 2 songs on my phone, weird bug. So if I want music I just downgrade to iOS 6 and put it on, if I'm contempt I upgrade back to iOS 7 but for now i'll just stay on iOS 6, until beta 3 comes out