Fuzzyband has been upgraded to support the latest baseband 05.13.03 in iPhone OS 4.0 Beta. The following instructions will only help downgrade iPhone 3G which is currently on iPhone OS 4 Beta with 05.13.03 baseband and older bootloader 05.08. This wont work with iPhone 3GS.

A complete step-by-step guide on how to downgrade baseband version 05.11.07 to 04.26.08 for iPhone 3G in order to unlock it with ultrasn0w on iPhone firmware 3.1.