Basically my iPhone 4 is pretty much having the same issue as this iPod Touch. http://www.youtube.com/watch?v=_91yEGFDozM I was attempting to downgrade from iOS 5 with the help of redsn0w and TinyUmbrella. Unfortunately now my iPhone 4 is stuck at this blackscreen when I perform a tethered boot. If I don't perform a tethered boot, iTunes will just recognize the device as in recovery or dfu mode. When I perform a tethered boot iTunes will recognize it as in 4.3.5, when I try to update it to 5.0, I get the 1600 error. If I attempt to call my iPhone, it will ring but obviously I can not slide it to answer it nor will the screen work. Any help would be greatly appreciated. Thank you.