I have had a hard time jb my 3g iphone... I had to have at&t reset the network and reregister my sim card because it was knocked off the network after i jailbroke the phone.

My question is: are you supposed to remove the sim card when jailbreaking or does it not matter? and are some iphones genetically predisposed to being jailbroken? (i ask because this is the 2nd time that I've tried to jailbreak and this end up happening to me - same phone)