I have a 3gs running on 3.1.3 baseband 5.12... I want to upgrade to firmware 4.0 and jailbreak with the new jailbreakme tool that came out yesterday. I tried installing the new firmware through itunes and i get an error message(error message 4). I've never had this problem before, i tried putting the phone on DFU mode and nothing. I have the latest version of itunes as well. Anyone have any ideas???