I tried to downgrade an iPhone 3G from the ipad 6.15 baseband. Everything seemed to go fine until the final reboot. The phone would not find the carrier and was on the 'slide for emergency' screen. I could not get past that screen to try to remove ultrasnow/mobile substrate (saw that on a youtube tutorial). The only way I could get back to where I could work with the phone was to replace the ipad baseband. Anyone figure out a fix?