after spending several hours on the internet trying to find fixes i have given up :(
after my 3gs broke last night i tried restoring it. pwange tool would recognize that the device is connected so i made custom firmware then did the whole thing on my pc. itunes kept giving me error 1600, after some googling i was advised to use ireb. boy do i regret that now. i used ireb to put in dfu. then did a custom restore to 3.1.3
now the device is stuck in dfu loop. i tried tiny umbrella and ireb but nothing!!! please someone help me i am completely desperate.