Go to C:\Windows\System32\drivers\etc\ and locate hosts file. Note: Win 7 and Vista users MUST run Notepad with admin privileges.
Right click on Notepad app and select Run as Administrator. You should now be able to successfully restore the desired older firmware (if SHSH saved).
Add the # symbol and a space ("# ") to the beginning of the gs.entry. For example, if you're restoring at work, try to restore at home or on a friend's computer and network.
Try to restore or update on another computer with a different Internet connection.
If you experience the error on your i OS device, here’s how you can quickly resolve it so that i Tunes will function with the restore or i OS update as intended.
Windows If you’re using a Windows computer, follow the steps from the Microsoft support site. Errors 1639, 3000-3020, and 3100-3999 (with the exception of 3194) are sometimes caused by your network settings.
Resetting the hosts file affects software services that rely on hosts file redirects. Enter the password you use to sign in to your computer and press Return. If you don't see a window similar to the one below, make sure you're using a nonblank administrator password. Navigate using the arrow keys and look for an entry containing “gs.apple.com”. If your computer uses a managed network, refer to your network administrator.
*** If you’re getting i Tunes error 3194 with the latest firmware (Signed i OS) then simply remove the Cydia’s SHSH server IP, if it’s already in the Hosts file. You can do this either by using Tiny Umbrella or you can also manually edit the hosts file. To add Cydia’s SHSH Caching Server to the Hosts file: Download Tiny Umbrella; Launch Tiny Umbrella, go to the “Advanced” tab and check “Set Hosts to Cydia on Exit”; Click on “Apply Changes” and then reboot your PC/Mac.
Put your i Device into DFU Mode and Try restoring it via i Tunes.