I have an iPhone 3.1.3 (baseband 5.12) that I CANNOT upgrade beyond 3.1.3 at all. I get error 1604 most commonly, I've done everything I can think of (new USB port, new USB cable, new login identity, Windows 7 machine, different Mac) and all give the same error. I jail broke it after all that and it took the jailbreak just fine, but now what! I want to get at least 4.1 on it, if not 5.0.1--official is fine, don't care about the jailbreak, I just want it to take the upgrade!! HELP!