As we reported earlier, Ultrasn0w 1.2.4 adds support for iOS 5 on a preserved BaseBand. You can preserve BaseBand of your iPhone 4 or iPhone 3GS by building a custom firmware through Redsn0w 0.9.9b5. Due to the fact that JailBreak is tethered, there is no Pwnage tool for Mac right now. It means that Mac owners need to create custom firmware using Redsn0w 0.9.9b5 only. Currently, BaseBands 04.26.08, 05.11.07, 05.12.01, 05.13.04, and iPad BaseBand – 6.15 are supported.
If you are on iOS 5 with BaseBand 6.15, you need to follow a trick. At the start of the instructions to setup your device, don’t turn on ‘Location services’ if it asks you to do so . However, these location services can be turned on from the settings.app again after the completion of the setup. Just enable ‘Find My iPhone’ and everything will be back to normal. If you are one of those iPhone 3GS (BB-6.15) owners who have upgraded to stock ipsw accidentally, your iPhone must be in an inconsistent state.
Now, we have a solution for you to come out from this inconsistent state. Just reflash the 6.15 BaseBand again using Redsn0w. Interrupting in between the process can cause serious problems. So, please do at your own risk. Note that this would not unlock your upgraded BaseBand on iOS 5. Instead, it would only unlock your iPhone on preserved BaseBands without any issues.