iPhone dev team has released RedSn0w 0.9.6 RC9 for untethered jailbreak support for iOS 4.3.1 on iPhone 3GS, iPhone 4, iPod Touch 3G, iPod Touch 4G and iPad1. The only iDevice that cannot be jailbroken with this update of RedSn0w is iPad2.
Devices supported by RedSn0w 0.9.6 RC9
* iPhone 3GS / 4G.
* iPod Touch 3G / 4G
* iPad 1 ( iPad 2 is not supported)
* Apple TV 2G.
Ultrasn0w is not compatible with iOS 4.3.1 . So, Ultrasn0w unlockers should excuse this update.
Download RedSn0w 0.9.6 RC9 for Windows and Mac