ok a few question and maybe a step by step to help you since i had a same promblem with a bad flash of CM9
1A. Can you boot into Recovery ? if not i can help you reflash your phone with the Kdz files took me forever to get it to work but i finilly found all the files needed.
1B. if it does boot into recovery run adb devices ... does it show the phone in recovery mode ? in the list.
If so then you can Download the following 6 files Dropbox Down link
its not mine but was posted in another Nitro Recovery topic i will give credits once i re go threw the topic to see the poster
in your CWM recovery go to mounts or it may be under advanced and turn on usb mass storage and as long as all of those files are in your adb folder you can run the pushall.bat and it will place them on your sdcard.
After that turn off usb mass storage and run adb devices again to make sure you phone is still showing up. If so run these commands
****** notice the SU command isnt used here**** cant get super user in recovery but it will still let you run the commands and i can confirm it does work
dd if=/sdcard/boot.img of=/dev/block/mmcblk0p8
dd if=/sdcard/recovery.img of=/dev/block/mmcblk0p13
dd if=/sdcard/firmware.img of=/dev/block/mmcblk0p1
dd if=/sdcard/system.img of=/dev/block/mmcblk0p27
dd if=/sdcard/baseband.img of=/dev/block/mmcblk0p14
You won't be able to issue a reboot command, so just hold power down on your phone til it's off and hold the volume down button so that it comes back up in factory data reset mode. You will want to pull your sdcard at this time if you don't want your data erased.
Hit power twice and your phone should go through its reset process and (hopefully!) come back up in a working (and rooted) AT&T "stock" rom
if not then try to follow this for the CM9 Adb Drivers Wiki for CM adb drivers
i know its a little work but it dose the trick then go back up to the previous step and try that to get to stock rooted
i dont think i left anything out but i can help with anything else i know if that doesnt get you back up and running.
Credits to ???? for the drop box link with the godly files for our nitro
and to Malnilion for his guide on unbricking the nitro