What other Airport card troubleshooting did you do before tinkering with your Open Firmware?
Did you ever reset the PRAM?
DId you ever back-up?
Did you reseat the Airport card?
Was the antenna connected?
Your directories must have been on the way out already, and in need of repair, before the NVRAM episode. Resetting that does not usually result in a disaster, but as you can see, it sometimes does.
It may be that the only way out of this is to boot from an external device, HD or CD, and see what you can recover from the damaged HD. Does DW reach a point that will allow you to review the drive before it says it is too damaged to repair? If it does, this is the time to drag the stuff onto another drive.
I switched an Airport card from one G4 tower to another (swapping from one Airport base to another). The one I installed into did not recognize the card. Simply put, "The card is not installed". I did a search on troubleshooting with the Airport card and found that all I would have to do is reset the NV RAM (not the PRAM). Once I did that, it only tries to boot on sys 9 (not even all the way, it just freezes up). Now Disk Warrior says the disk is too severely damaged to rebuild OSX. What would cause this? Any suggestions out there?