I have the exact same issue with my Samsung 5.1 surround sound system and like X1, i've only been able get it working on 2.1
It would be awesome if anyone has any suggestions for workarounds that actually enable us to enjoy playback on 5.1
I have actually encoutered this problem while backing up and restoring iphones in one of my previous jobs. This is a bug with iTunes and unfortauntely you won't have access t oyour data. I suggest performing icloud backups of your information in future.