The iPhone Dev-Team has released UltraSn0w 1.25 which brings iOS 5.0.1 support to the unlock for older compartible basebands.
iPhone Dev Team’s iPhone 4, 3G, and 3GS software unlock, now with added PwnApple. Compatible with iPhone 4 baseband 01.59.00 and iPhone 3G/3GS basebands 04.26.08, 05.11.07, 05.12.01, 05.13.04 and 06.15.00! Thanks to @sherif_hashim and @Oranav for contributing baseband crashes
If you have one of the supported basebands and wish to update to iOS 5.0.1 you will need to do so with a custom ipsw that doesn’t update your baseband.
Indeed DevTeam have not updated software unlock utility ultrasn0w to work with the latest iOS 5.0.1. There are two workarounds, that will make ultrasn0w work on 5.0.1.
The iPhone Dev-Team has released an update to their UltraSn0w unlock bringing support for iOS 5. Remember that NO new basebands are supported in this release. It only adds support for iOS 5 with old basebands.
Here is the list of supported basebands:
If have one of the above baseband version and need unlock you can upgrade to iOS 5 without updating your baseband using RedSn0w 0.9.9b5.