hi, i have an iphone 4 and i wanna update it to iOS 4.3.1, whenever i plug my iphone to my mac itunes opens then a windows asks me if i wanna download or download&update ! i choose download because my internet connection during the day is somehow not that fast. So i usually update my mac and my iOS devices at night. so when the update starts, everything goes fine until it reach a point really close to the finish line and an error window pops out like the attached picture. i even tried to download the update on another computer on even a better internet connection, and the same error is coming out. how can i fix that?