The newly released iOS 4.1 for iPhone 4, 3GS, and 3G features new baseband which is currently not unlockable using the current version of ultrasn0w. But if you upgrade (while preserving baseband) and then jailbreak iPhone 3GS on iOS 4.1 using PwnageTool method posted here (www.redmondpie.com), you can unlock your phone (iPhone 3GS) using the existing version of ultrasn0w. Also, if you upgrade your iPhone 4 (while preserving baseband) on iOS 4.1 using the method posted here (www.redmondpie.com), you will be able to unlock your phone (iPhone 4) as soon as the new jailbreak tool is available for download.