If you are on 3.1.3, jailbreak with Spirit, and unlock with Ultrasn0w. Bootloader doesn't have any effects on unlocking at this point.
redsn0w works great. but i keep on getting Invalid SIM error. does this mean that I lost my unlock?
i did that last nite, officially upgraded to 4.0 then used redsn0w to jailbreak it. and its so slooow having iOS4 on the 3G. i tried to unlock it after it had been jailbroken but nothing. so today i downgraded to 3.1.3 and user cellular data network it says "SIM not provisioned"?