Trouble processing file in iOS4 update, tried EVERYTHING! PLEASE HELP

I downloaded iTunes 10.5, I troubleshooted the problem and I've tried everything in the books. When I'm downloading the file, it goes for about 45 minutes without a problem, then when the update reaches the point of "processing file", a screen pops up that says "network connection timed out". Please help, this has been a problem for me for about 3 days now.