Quite a few members of the Jailbreaking community backup their SHSH blobs to Cydia’s server for downgrading purposes ever since the release of iOS 4.3.3, the people who have edited their hosts file to point to Cydia’s server instead of Apple’s have started to face problems even while upgrading to the newer firmware. So if you’ve edited your hosts file that way you wont be able to restore to a Custom or even a stock firmware, iTunes will just show you the error 3194. This is the message you’ll see.
[box] The iPhone could not be restored. An unknown error occurred (3194).[/box]
This problem is apparently caused due to a bug at Cydia’s back end and should be fixed soon. However, until that happens you can fix this problem in just a few simple steps. Now, to do this you simply have to remove the reference Cydia caching server from your hosts file and this is how you do it:
* Download TinyUmbrella from http://thefirmwareumbrella.blogspot.com
* Launch it.
* Click on the “Advanced” tab.
* Uncheck “Set Hosts to Cydia on Exit”
* Click on “Apply Changes”
* Reboot your PC/Mac.
You should now be able to successfully restore or update your iPhone to iOS 4.3.3 firmware.