Yesterday, the stupid Bing application from M$ crashed my unlocked iPhone, then somehow damaged my unlock. My iPhone couldn’t reboot. Even blackra1n couldn’t re-jailbreak the phone. I tried many ways, read dozens of articles, but all failed. I decided to restore my phone. Then serious problems occurred.
First, iTunes asked me to restore and UPDATE to the newest firmware, which I know for sure is not yet jailbrokable. So I option-clicked the “Restore” button to select the 3.1.2 firmware file that I downloaded for restoration. iTunes reported an error that my phone is not eligible for requested build, which basically meant that my phone could not be restored to 3.1.2.
Fortunately, I already have the SHSH (hash signature) of my phone on the Cydia server. I then followed the instructions on this page to fool iTunes of the Apple server. The restoration process went smoothly. My phone was restored to 3.1.2, then was jailbroken with blackra1n. Everything is back to normal. So I strongly suggest everyone who has a jailbroken/unlocked iPhone to upload the SHSH of their phone to the Cydia server.