[xz mage pker]

hey guys. i have an i phone 3g and i restored it in my itunes (version 4.1.2 modem firmware 5.15.04) the problem is when i try to jailbreak it with redsnow the section when it tells me to put it in dfu it wont work. i cheeked the cables on the phone works fine. same with the home button. i can restore it with itunes and i tried putting it in bootmode or recovery then jailbreaking it. it doesnt work. its say waiting for phone to boot in redsnow.

any ideas?
thanks