It is entirely possible you have a bad card. I installed a brand new one fresh out of the box for a client a couple of weeks ago in a 14" iBook. Didn't work first time, so thought I hadn't installed it correctly -- unlikely, given that I pop these babies into different Macs several dozen times a week. Reseated it, still nothing. Opened up another box, installed the AE card and was away first time.
I've also had this happen with the older Airport cards, although usually after a year or two of use. It seems they just die.
Send it back and ask for another one...