All of the guides I have read that cover downgrading from a jailbroken 1.1.3 (via Nate True's jailbreak) to a jailbroken 1.1.2 either give the instructions on how to do so via a Windows PC (I am on a Macintosh), or they describe doing so for phones with bootloaders 4.6 and up (1.1.2 Out of Box and later)...mine is bootloader 3.9 (I believe)

As I said, I am using a Macintosh, have the latest version of iTunes installed, have a jailbroken 1.1.3 iPhone (via Nate True's jailbreak), my modem's firmware is 04.01.13_G, and the first couple digits of the serial number of my iPhone are 7T725xxxxxx (which I believe means it was one of the iPhones from the first batch that shipped - week 25)

Jailbreaking my iPhone with 1.1.3, and then subsequently trying to fix the Google 'Locate Me' feature of the Maps.app with a lockdownd file that was most likely the wrong file has really screwed up my phone (no wifi, etc, etc.), and at this point I desperately need to know what the absolute simplest way possible is to downgrade my iPhone to a jailbroken 1.1.2 firmware, so that i can then apply the newer iphone dev team release of the 1.1.3 jailbreak)...

As noted here, in comparing the iPhone Dev Team's 1.1.3 release VS. Nate True's 1.1.3 release:

Supposedly NateTrue's method will break functionality needed to support official 3rd party apps when they come out in February, so it is a good idea to use this method instead.

PLEASE HELP!!! I need to know the simplest, Macintosh/jailbroken 1.1.3 iPhone/bootloader 3.9 compatible method to get back to jailbroken 1.1.2 (to then apply the newer iPhone Dev Team 1.1.3 jailbreak)!!

Any suggestions would be greatly appreciated... Thanks so much!

i found this helpful. Used it twice. http://hackthatphone.com/113/iphone_downgrade_113.html