First of all this is not a new Unlock. If you come over in order to see if this is a new Unlock for iPhone 4, so don’t waste your time. Go over here and see the perfect solution for the Unlock for iPhone 4.
Recently the Untethered Jailbreak for iOS 4.3.1 was out an Ultrasn0w was broken on iOS 4.3.1 and was not working. Today ih8sn0w and MsftGuy released the fix for that issue. This is the method to Fix Utrasn0w on iOS 4.3.1 on old basebands which are 1.59.00, 5.12.04, 5.13.04,6.15.00,4.xx. Below is the complete guide on how to fix the Ultrasn0w.
To follow the steps and to Unlock you need to be Jailbroken on you iDevice.
Steps to Follow:
Add this repo in Cydia.
Search for Ultrasn0w Fixer for iOS 4.3.1
Install the Ultrasn0w Fixer for iOS 4.3.1
If you got the old ultrasn0w Fixer by DjayB6 for iPhone 3GS installed, It will remove it and install the Current one.
Once installed enjoy!