Here is the guide that will allow you to unlock this terminal without running into the error that prevented the progress of the process after the entry into Recovery Mode.
Firmware 3.1.2 installed on your device (downloadable from here or directly from iTunes)
Note: Once you reset the firmware you need to make a restart of the device to ensure the successful operation of Jailbreak the iPhone.
1. After downloading blackra1n, move the executable in the directory “C: /”.
2. Shut our iPhone 3G and make sure that the USB cable is attached to the device.
3. We initiate blackra1n and press the only button available “ra1n make it.
4. We turn on our iPhone via the Power button and wait until you start. In this passage might open several times iTunes: just close it only via the dedicated button.
5. We expect the successful entry of your iPhone in Recovery Mode (step strictly done by the program itself) and then, after the disappearance of the image that portrays GeoHot, we will be in a LockScreen with our iPhone jailbreakkato.
6. We go into “Settings> Wi-Fi” and insert the password (if any) of our Wi-Fi home network. We enter, therefore, in the new application installed, blackra1n. With a tap select the package “Cydia” and then the button on the top right “Install”. Done!
Finally you can enjoy the iPhone 3G unlocked, avoiding the annoying error on the Recovery Mode.
If the method just presented their works there, try to follow this exposed by Anna:
1. Connect the iPhone to your computer, close iTunes and click on “Make It Rain” by blackra1n.
2. When the iPhone crashes in recovery mode, and blackra1n remains in “running”, do not close BLACKRA1N and turn off the phone by clicking on Home + Power.
3. The program will tell you that the operation of Jailbreak has been completed but in reality it is not. At this point, then:
Click on the Make it Rain
Turn on your phone
The program should recognize the iPhone and completing the Jailbreak.