For those of you (iREB didn't work for me either when I first jailbroke) that iREB isn't working, I have a simple solution. Just download redsn0w and upload the firmware it requires. Next, connect your iDevice and follow the steps to get into DFU mode and as soon as you see your screen turn white (or red?) disconnect your device, and close redsnow. Reconnect, open up iTunes and then restore your custom IPSW! Everything should work fine, if not try another time or two.