Need some help quick flashing ROM through SafeStrap topic

I'm trying to flash a ROM on a i337 S4 running 4.4.2 NB1, I have it rooted SuperSu installed and Safestrap custom recovery install. I boot into recovery create a new ROM slot (standard sized) flash ROM, flash NB1 modules, flash SuperSu (per ROM's instructions) then reboot. Now heres the problem, it will boot show Safestrap and the Samsung boot but right after that where you would normally see the AT&T boot or the ROM's boot it just goes black. Black screen nothing there no button press work nothing, I know the phones on because if I have it plugged into the computer through USB it will recognize it as an Android device. I let it sit for a good 10 minutes and nothing. Has happened on a couple different ROM's. The one I'm currently trying to flash in Empty Galaxy http://forum.xda-developers.com/show....php?t=2768183