I have updated my iPhone 4 to 4.1, and then ran Limera1n to JB. When the Limera1n icon comes on the screen, the little "processing" circle shows up and I when I tap it nothing happens, and then the phone shuts down. When I restart the phone I do not have a Cydia icon.
I am running IOS 4.1 with Baseband 01.59.00. I did save my SHSHs with TinyUmbrella.
I was running into that problem and the only way I was able to have a sucessful jailbreak was by opening itunes and leave it open while you jailbreak with limera1n
I was able to get this fixed. I got a custom fw from westonben, and was able to restore to that and then JB. I never was able to launch the limera1n icon, but Cydia was installed. I'm all good now. Thanks for the suggestions.