Hello, everyone. I was the second person to post on this thread, and I haven't posted much lately, since finding my "workaround" of not letting the iPhone 6 sync to iTunes — not a permanent fix, obviously, but it has served my needs till this gets straightened out.
This morning I noticed Soulnational's posts about authorized computers and associated devices, which was greek to me. So I started digging around. On my iMac, in iTunes, I went to Store > Account > Manage Devices, and I found that the list refers to my iPhone as "iPhone (Mike's iPhone 5) associated September 19, 2014." That's the day the new iPhone 6 arrived, and I set it up through a backup. Standard procedure. In the old phone's settings, I had named it "Mike's iPhone 5," so that nickname was carried over. Now, bear with me.
Later that day, I went to connect the new phone with the Bluetooth in my car, and when the car was searching for devices to "discover," I noticed that the car was recognizing the new phone as "Mike's iPhone 5." Being a stickler for precision, I went into the phone's settings and changed the nickname to "Mike's iPhone 6." The car then discovered it by that name, made the connection, and all was well.
Till the next morning. After the phone recharged overnight and did the auto-sync to iTunes, that's when all the trouble started.
Is there perhaps a commonality here? Have others who posted here also changed the nickname of their new phone — after initially setting it up from a backup, with an old nickname? Might this be the root of the problems we're having. Note: as of right now, I have not changed ANY of my settings. I'll wait to get some feedback. Thanks.