Apple released iOS 4.0.2 in response of jailbreakme pdf exploit, so as of today, Apple has stopped signing 4.0.1 restore files. That means that if you have a iPhone 4 / 3GS you cannot restore any firmware other than iOS 4..0.2 If you guys updated to iOS 4.0.2 and wanna go back to iOS 4.0.1 here is the step by step guide to downgrade your iPhone 4 / 3GS iOS 4.0.2 to 4.0.1 or below. This hack can be attempted only for those, who saved their SHSH to Cydia Server ...