Have you tried the acclaim_update.zip file? Put it on the root of the SD card, put the SD card into the NT, and power it up, and that should
do a full restore back to stock 1.4.0.
[Stock Firmware]Restore Barnes & Nobel Nook Tablet 16G 1.4.0 from SDCard - xda-developers
I used it when I was doing the root on my NT, although mine never bricked. If that doesn't work, maybe go over this thread and see if there's anything you missed or new you can try:
[UNBRICK] Repartition, Reformat, Restore and Rescue SDcard - xda-developers
Hope one of these can help! And welcome to the forums!