If you have your iPhone 3G/3GS flashed to iPad baseband 06.15.00 to retain the ultrasn0w unlock, and now somehow managed to make your phone unbootable here is the solution.

While trying to resurrect an Apple iPhone 3G stuck in a reboot loop at boot logo, I found that the only solution is to go for an factory unlock service and restore to the original iPhone iOS firmware with current modem version. Apple needs the correct baseband/modem version to enable the legal factory unlock via iTunes, and if you have the iPad baseband 06.15.00 it wont work. Here is a tutorial on how to downgrade the iPad baseband 06.15.00 to the correct one on Apple iPhone 3G.

If you are one of the unlucky few who rely on an carrier-unlock for iPhone 3G and accidentally updated to iOS 4.1 upgrading your baseband (modem) to v 05.14.02 which is not unlockable, here is a method to let you upgrade your baseband to one of iPad 06.15.00 which is fortunately still vulnerable and will allow us to unlock using ultrasn0w.

In this comprehensive step-by-step illustrated guide we will walk-trough the complete process of jail-breaking and unlocking an iPhone 3G running iOS 4.1 having modem version 05.14.02.

There is nothing exciting or worth upgrading in iPhone OS Update 3.1.3 but if you still want to upgrade and keep the jailbreak it is now very much possible thanks to updated redsn0w 0.9.4 utility by iPhone Dev Team, do keep in mind if you are using an unlocked iPhone do not upgrade as no unlock is yet released for iPhone OS 3.1.3.

Just moments ago iPhone Dev Team released the redsn0w 0.9 public beta download for Windows and Mac, supporting the latest iPhone OS 3.1.2 the cross-platform jailbreaking and unlocking utility for iPhone and iPod Touch also supports customizations like changing of device boot logo, recovery logo, and allows users to switch on “verbose” booting mode.

The free standalone utility does not use iTunes and no custom IPSW's are involved in the process, the current beta supports all iPhones and iPod touches except the iPod touch 3G having Apple firmware 3.0 and 3.1.2, direct download links are at the end of this post.