The error in iTunes (3) is related to other errors involving security software. If you have software on your Windows PC, you can't just turn it off. In most cases, you have to uninstall it to overcome this error. The Apple Update server uses specific ports that may be blocked by security software. When you only suspend or turn off the software, these ports are stil blocked. By removing the software, you will completely unblock them. Common errors: 2, 4, 6, 9, 1000, 1611, 9006, 9807, 9844. Sometimes as a result of this issue, a device might stop responding during the restore process. TS3694 goes through most of the errors. Error 3 is relatively new, but falls in with 2, 4, 6, 9.