Fix Error 37 and Jailbreak Failed: Service Wouldn’t Start after downgrading A5/A5X Device
Earlier today we posted a method to downgrade A5 and A5X devices. Since then, we have been hearing of a few errors either with the downgrade method itself, or with jailbreaking after finishing the downgrade process.
The first error happens during the downgrade process, iTunes Error 37. I still have not been able to determine exactly what causes this error, but there are a few tips I can give you to try and solve the issue. First of all, if you are a Windows user, make sure you are running Redsn0w as administrator(you should always do this when running Redsn0w on Windows). Another thing you can try is use the opposite SHSH source that you used on your first try. For example, if you used the "remote" Cydia SHSH the first time, try using the local TinyUmbrella SHSH the second time. Finally, make sure you are selecting the firmware in the correct order(first select the 5.0.1 firmware and then select the 5.1.1 firmware).
The second issue is happening to people after they've downgraded and once they've attempted to jailbreak. The error during jailbreaking is Jailbreak Failed: Service Wouldn't Start (642). I have determined that this issue is being experienced by people who restore their device from a backup BEFORE jailbreaking. If you are experiencing this issue, don't worry you do not need to restore. Just go to settings>general>reset and select "Erase all Content and Settings." Once that's done you should be able to jailbreak(if it doesn't work the first time do Erase all Content and Settings again). Once you're jailbroken, then you can go ahead and restore from a backup and you should have no issues!
Thanks to @CovXX for helping me with this post.
If you have any additional issues you would like us to address or you have different solutions to these issues, please respond in the comments section!