HELP! Can't enter dfu mode
Hey guys, please help, this is driving me mad!
I'm trying to jailbreak my iphone 3g, it's on OS 4.2.1 and I've been trying use greenpois0n but when I try to enter dfu mode it just goes into recovery mode. I've tried this LOADS of times, I'm getting the timing ok I'm sure (I follow the countdown on greenpois0n) but every time the screen just goes black and I have to restore it in itunes.
I've tried different usb ports, running greenpois0n as administrator but I get the same problem everytime.
Any idea's? I'm using windows 7