crwdns2890332:0unknown error occured 1671crwdne2890332:0I had the same issues and it ended up being iTunes was still downloading software for the update. I don't have a clue why it prompted me to continue the update when it was still downloading. Look in the upper right-hand side of iTunes for the square box which has the downloading indicator on it. Make sure it's still not downloading before reacting to the prompts. Once it was done, I was clear for takeoff! Hope this helps some of you.