Default Unlocking one x from cm10.1

First off, I am runnign cm10.1 nightly and I have gotten an unlock code from AT&T. I was following this

http://forum.xda-developers.com/show....php?t=2395697

And it told me that i needed to get a stock rom before using the unlock code. So i tried to install this

http://forum.xda-developers.com/show....php?t=2181891

But when I flash, wipe delvik and cache, and system reboot it goes to a black screen. And oddly enough a white bar blinks on top every once in awhile. I'm not quite sure what to do. I can go to bootloader but thats about it..