When you jailbreak your iPhone with PwnageTool 3.1.4 and then unlock with Ultrasn0w you may notice that you carrier logo is missing even your iPhone works normally. To fix this bug iPhone Dev Team has released a patch so now you need to upgrade your unlocked iPhone OS 3.1.2 through this new Ultrasn0w 0.92 to bring back your carrier logo on your iPhone screen.

You can get upgrade to Ultrasn0w 0.92 from Cydia whereas Ultrasn0w just works to unlock iPhone 3G and iPhone 3GS with baseband 04.26.08.