Steps that worked for me to jailbrake my iPhone 3G 3.1.2 using #blackra1n

3G support in Blackra1n is "flaky", as GeoHot himself said on Twitter.

I tried several times and following different procedures described in related forums, but I always ended with the iPhone in recovery mode.

Until I found a sequence that worked for me in this post :

1. Plug the iPhone in the computer.
2. In iTunes uncheck the option "Automatically sync this iPhone when connected".
3. Close iTunes.
4. Optional: Several posts recommend to kill the iTunes/iPod processes, but I didn't see a difference doing this.
5. Start Blackra1n and press the button "Make it rain".
6. You should see the iPhone going to recovery mode (USB and iTunes logo) and Blackra1n changing to "Running". If you see this for more than 30 seconds then the process has failed. This is what happens on iPhones 3G.
7. Close Blackra1n.
8. Start Blackra1n again, but DO NOT press the button.
9. Hold Power and Home buttons on your iPhone. Don't release the buttons, you must see the screen going black,
10. After some seconds you must see the Apple logo, release the Power button, holding the Home button.
11. Don't release Home button, you must see the recovery mode logo (USB + iTunes) and then press "Make it rain" in Blackra1n.
12. Almost immediately you should see the GeoHot image instead of the Recovery mode logo.
13. Release the button, and wait for the process to finish. Once the iPhone rebooted you'll see the Blackra1n app to install Cydia or RockApp.

This worked for me,

Good luck!