As the dev-team promised about fixing ultrasn0w with iOS 4.3.1, MuscleNerd has uploaded a screen shot of ultrasn0w 1.2.1 which brings support for iOS 4.3.1 jailbroken iPhone 4, 3GS with old basebands. Some users has used ultrasn0w fixer but still have some bugs as they noticed a single signal bar.
Ultrasn0w 1.2.1 fix all these bugs. But you have to know that ultrasn0w 1.2.1 isn’t a new unlock, it will allow users to unlock iPhone 4, 3GS on these basebands only (04.26.08, 05.11.07, 05.12.01, 05.13.04, 06.15.00, and 01.59.00).
So who relies on ultrasn0w unlock and want to jailbreak his device on iOS 4.3.1, he MUST use PwnageTool 4.3 (Mac) or Sn0wbreeze 2.5 (Windows) to preserve their unlockable baseband while upgrading to iOS 4.3.1.
[machackpc]