iPhone developer iH8sn0w has just released a new version of iREB which is compatible with all iOS 4.2.1 devices. You can use it to bypass 1604, 1603, 1602, 1601, 1600 error in iTunes during custom iOS 4.2.1 firmware restore which has been created using either Sn0wbreeze or PwnageTool.
Some of you might have noticed the annoying 1604, 1600 error when restoring to iOS 4 custom firmware in iTunes which is built using PwnageTool 4.0 or 4.01. The error in question looks something on the lines of this.
