Earlier today I upgraded my iPad 2 to iOS 5 and it worked without a hitch. However, my iPhone 4 wouldn't upgrade. I kept getting an error message from iTunes that an internal error had occurred. I tried rebooting both the iPhone and my laptop, ensured I was running the latest version of iTunes (and OS X), but the upgrade would still bomb-out when iTunes first tried to restore my iPhone. iTunes would backup my iPhone, then try to restore it (which I really think was the "install iOS 5" step), and then give me that generic error message.
On a hunch, right after the iPhone had rebooted, but before iTunes started restoring, I swiped to unlock the screen and keyed-in my passcode. Et voilà! iTunes was able to proceed with the first restore (a/k/a install iOS5).
I hope that helps anyone else stuck on this problem!
I had a similar problem updating one of the kid's iPads. I think it had more to do with Apple's overloaded servers than anything else. All my other upgrades to iOS 5 and Lion went without a hitch.
Posted by: Steve Sarette | 2011.10.16 at 12:12 PM