I am just passing on information. Last night I updated the iphone, but it would not complete the update. The dialogue box asked me to restore and update which I did but before it could be restored iTunes resulted in an unknown error (1604). I called tech support who were VERY helpful. They are sending me a new phone. I have read others having problems with unlocked phones...I just wanted to pass on that I had trouble with an unmodified version of the iphone. Hope others fair much better!