I dont know why but I still can't understand jailbreaking 1.1.2 even from that page.....just for 3rd party apps, who cares about frigging unlocking.
Ok, Its really easy... I'll explain the process here.
Preliminary:
Download the readline library here
http://rapidshare.com/files/61509655/opt.zip.html and save it to your desktop.
In the menu bar hit Go > Go to Folder > type "usr/local/lib/" (without the quotes) and place the readline library folder in the new open finder window (lib). You may have to authenticate it, thats ok do it.
Download the Jailbreak program here
http://conceitedsoftware.com/iphone/site/112jb.html , and place the folder (1) on your desktop.
Here we go!
1. Install OktoPrep, from the installer.app on your phone. (Tweaks 1.1.1 Catagory)
2. Update your phone from 1.1.1 to 1.1.2 through iTunes. (Update, NOT Restore), and activate it likewise.
3. Go into the folder "1" on your desktop and open "jailbreak.jar". it will open a dialog box. At the bottom check the box that says "install SSH" and change the password if you want to.
4. Wait.... It's going to take a while and say things like "reading flash image, and writing flash image etc..." (If it say's "cannot connect to device" make sure that the readline library is in the right folder.)
5. It will say "Done", then all you have to do is reboot the iPhone, and when it turns itself back on and reboot itself one more time.
6. Now you have installer.app on your springboard, and you can install all of the things that you had before on 1.1.1.