Hey Kevin:
In short, don't do iCloud back-ups or restores from iCloud.
If you have music from anyother place than iTunes - say downloaded from other websites / share sites - this seems to corrupt your iCloud. Real freaky.
Anyways, just plug in your iPhone into your computer, via iTunes, wipe it clean by hitting "Restore" button. But when it comes back - don't restore from a previous backup - if you do, what was once wrong, will be wrong again.
Or you can follow the LONG instructions below.
[100% Resolution Confirmation:]
Hi everyone, So I've had this same issue plaguing me on both my iPad & iPhone. But along with some of the helpful suggestions on this topic and in this thread I was able to completely fix both my iPad and iPhone. So I'm going to reiterate what’s been suggested and what I exactly did in order to fix my devices.
The Issue:
When you plug your iPad/iPhone/iPod Touch into your computer to add new music in which you downloaded off the internet, you get random prompts to sign in under emails/apple I.D.s you've never seen before. Plus certain songs you try to add to your device will not sync or actually download onto your iPod/iPhone/iPad. It will even appear that they have properly been added but they wont actually be there or else will show as grayed out when opening your Music application on your device.
The Reason why:
With iCloud now available and wireless backup possible...any songs that you didn't buy from iTunes and instead downloaded from a torrent (in which someone else across the world uploaded to the torrent after they purchased and downloaded it from iTunes) is what causes this Issue. As previously mentioned in this thread...when a song is purchased on iTunes then available to be seeded from your computer, anyone who has iCloud backup enabled and downloads the song will be prompted by iCloud to sign into the original purchasers Apple ID account. This is I guess another step in the fight against illegal downloads.
Resolution: (Works on all 3 devices. *Tested, Tried & True*)
Step #1.- On your iPhone/iPad/iPod Touch... Go to Settings > iCloud > Storage & Backup > iCloud Backup (Turn this Feature from 'On' to 'Off') *Note* This does not mean that you still can't use iCloud to share your notes, photos, emails, Calendar between all of your devices. This can still be used and left activated. You just can't no longer Backup to iCloud.
Step #2. -Plug your iPhone/iPad/iPod Touch into your computer and when it displays your device on the screen along with all the details on remaining space etc. Click the option that says 'Back up to this computer'. Make sure that your computer is no longer backing up to iCloud.
Step #3. -Delete/remove all your music from your iPhone/iPad/iPod and make sure that its completely clean of the 'Corrupted files' that are prompting you for an unknown Apple I.D. user. (This kind of ***** I know to remove all your music but believe me this will fix your Device! And you can always put all your music back on from your computer).
Step #4.- Now that you have cleaned your Device you want to back up/save all your Apps, Notes, Photos, etc. So in the bottom right hand corner click the button that says Sync. This will ensure that iTunes backs up all your important stuff (Apps, Photos, Notes etc) to the actual computer so you don't lose it all during this repair.
Step #5.- Once the Sync/Back up is complete you now have to click the option "Restore to original settings". This will bring your iPhone/iPad/iPod Touch back to original factory settings but also run the newest update so your device will be current with the newest operating software. This restore will take upwards to 10 - 15minutes.
Step #6.- When the restore is complete you will be prompted on iTunes on whether you want to start as a new iPhone/iPad/iPod Touch or whether you want to restore the device from a previous computer back up. Please make sure that the back up you do has the correct date/time on it! When you choose the back up it will the current date & time that it was last backed up. Once you've found this allow it to sync and reinstall all your apps, photos, notes, etc.
Step #7.- Now you can re-add all your music & videos, providing that your iCloud Backup is still selected as 'Off' in the settings menu and your iTunes is 'Back up to your computer' and not 'Back up to iCloud'.
And there you have it...your device will no longer prompt you for the unknown Apple I.D.'s and all your music will properly add onto your iPhone/iPad/iPod Touch!
As I mentioned this is a 100% guarantee fix, I just did this last night to both my iPhone4 and iPad 3. I hope this helps anyone out with this problem and provide a little less headache! If you have any questions please just reply to my post!
Take care!