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.