I just got an used iPhone 4 (4.2.1_8C148) from an american friend of mine. I live in Brazil so I don't get warranty, genius help, anything. It is locked to At&t so last night I jailbroken it with redsn0w. Reading a tutorial, I found a better way to unlock it with ultrasn0w. So I decided to restore it and do the jailbreak again, this time with ultrasn0w. I restored it on the iPhone itself (not in iTunes), but it never turned on again. It gets stuck on the apple logo (for more than 6 hours!) So the only way out I found was to recover on iTunes. But I heard it is not possible to unlock the 5.1 version yet. What should I do? iTunes is downloading the 5.1 version to start the recovery right now. I'm not really sure I should do it.