Dev Team recently released Ultrasn0w 1.2 to unlock iOS 4.2.1 which required to upgrade iPhone with iPad 3.2.2 baseband 06.15.00.
Users who tried this method to unlock their iPhone informed that they are now having GPS issues.
Please note, that unlocking the iPhone using ultrasn0w 1.2 after upgrading using pwnage tool unlock edition or redsn0w beta 5, both cause this problem of significant loss of GPS signals.
Dev team has also spotted this issue and included it as an update in their official blog saying:
Update # 5: Unlockers have been reporting mixed results about GPS functionality at 06.15.00.
Until we can track down what differentiates those who retain GPS vs. those who lose it, be conservative and assume you’ll lose GPS at 06.15.00.
As we work on finding the cause (and possibly a fix), please report your personal findings in our comments section.
(Update: early indications are that while 06.15.00 is capable of GPS, it will require some further hacks. But please still be conservative and assume you will lose GPS at 06.15, in case the hacks don’t work).
Please note, these hacks may not work ! so don’t upgrade to baseband 06.15.00 unless you are certain what you are doing and have no other option!