Trying to update iPhone firmware and it's making me download update all over again!

Hi all,

Alright so I am trying to update the firmware on my iPhone 4 which currently has iOS 5.0.1. I plugged it in, opened iTunes, and clicked update. I went through the agree/disagree and the "backup/don't backup" popups Then, iTunes started to download the firmware update. After two hours of download time, it finally finishes. I unplugged my iPhone to make a call, then plugged it backin to go ahead and install the update. I go to my iphone on the left hand column of iTunes, click update, go through all the same popup windows and then iTunes stars to download the entire update all over again!!! I even checked the library directory where iTunes downloads the firmware/restore files (.ipsw files) to, and notice that the original update file is still there (iPhone3,1_5.1.1_9B206_Restore.ipsw), and it is downloading the exact same file all over again. Why is it doing this? I don't want to have to wait another two hours!

Thanks for any help,

James