3g jailbreak problem
 

set got in apple logo , tried with 4.2.1 and 4.1 always error but successfully flashed with 3.13 3g firmware using itunes 10.1.4 . phone now in 3.13 and 6.15 firmware, when try to jailbreak with redsnow latest selecting 4.1 firmwarwe after uploading second stage and then reebooting phone always power on and never get pineapple logo or downloading jailbreak data, please help to jailbreak this phone