Many users have accidentally upgraded to firmware 2.2.1 on their devices and they have lost their jailbreak. People repeatedly keep asking how to downgrade firmware 2.2.1 to 2.2 in the QuickPWN Forums.
vicon-sd posted a great guide on how to downgrade in the forums at this topic:
Upgraded to 2.2.1? Here’s how to downgrade!
Here is how you can downgrade from firmware 2.2.1 to 2.2:
* Connect your iPhone to your Mac or PC and select your iPhone from the list of devices in iTunes. If things had gone horribly wrong while hacking your iPhone and iTunes does not detect your iPhone then you will need to put it in DFU (Device Firmware Upgrade) mode.
o You can follow these steps to put your iPhone in DFU mode (this is required only if iTunes does not recognize your iPhone):
+ Connect your iPhone to your computer.
+ Turn iPhone off.
+ Hold power and home together for 10 seconds (exactly).
+ Release power but keep holding home until the computers beeps (observed on a PC) as a USB device is recognized.
+ A few seconds later iTunes should detect your iPhone.* In the Summary Tab, Hold down Option and press the “Restore” button. If you are using Windows hold down Shift and press the Restore button. (This is an important step as just pressing the “Restore” button will result in restoring your iPhone with the latest firmware which is firmware 2.2 currently, by holding down Option in case of Mac or Shift in case of Windows, allows you choose the firmware file that you want to downgrade to.)
After restoring you can download the jailbreaking tool and jailbreak firmware 2.2.
