I have a totally stock iPhone 3G 8GB on the AT&T network. I just did a full restore using iTunes to 3.1.2. I'm running Windows XP and I have located several custom jailbroken ipsw files. EVERY TIME I do a 'shift + restore' I get ERROR 1604. When I attempt in DFU mode I get ERROR 1600. Any ideas what in the hell is going on?