If you're experiencing problems with upgrading to iOS 5 from iTunes try downloading the IPSW (iOS file) from the following links




iPhone 4 (GSM)

http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw



iPhone 4 (CDMA)
http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw


iPhone 3Gs
http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw


iPad 1
http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw


iPad 2
http://appldnld.apple.com/iPhone4/04...4_Restore.ipsw


iPod Touch 3gen

http://appldnld.apple.com/iPhone4/06...4_Restore.ipsw


iPod Touch 4gen

http://appldnld.apple.com/iPhone4/06...4_Restore.ipsw





How to install:


1. Locate and download an iOS 5 IPSW file from the web


2. Launch iTunes and Option-Click (Mac) or Shift-Click (PC) on the “Check for Update” button to restore the iPhone


3. Select the iOS 5 IPSW and proceed with its installation onto the iPhone