Apple released firmware upgrade (iOS 4.1 beta 2) for iphone on 28th July 2010. This upgrade primarily available to the developers at the moment cannot be unlocked with RedSnow. This beta build contains a new baseband 05.14.01_BL01 which cannot be unlocked according to a recent tweet from the Iphone Dev Team.
Users are hence notified to refrain from any fancy upgrades in order to retain their jailbroken device. To learn more features about new firmware upgrade iOS4.1 beta to , read here.