Comments for this post are now closed and the guide is made available for reference only. I have published my guide to jailbreaking and unlocking firmware 1.1.3, please refer to that to upgrade to the newer firmware version.
I have been messing around for a day or so trying to get this to work, but I think I’ve nailed the method for upgrading an unlocked and jailbroken iPhone to firmware 1.1.2, and preserving the unlock and jailbreak. What follows are the steps to get your iPhone to 1.1.2 written as simply as I could manage. These instructions look long (and they are), but they are easy to follow and anyone with basic computer skills should be able to get it done. Remember: there is no predicament that you can get your phone into that can’t be repaired.