Try downloading it to your desktop from our thread here -
http://www.iphoneforums.net/forum/i...ple-ios-firmware-download-links-iphone-22984/
Make sure you pick the right one for your phone!
Then, once the download is completed, open iTunes, and shift-click (Windows) or option-click(OSX) on the "update" button in iTunes and it will allow you to select the IOS5 file you just downloaded. That should avoid iTunes timing out.