I had something similar to this happen when I intalled an Airport Card in my father's iBook. I recall that the installation steps need to be followed very closely. It was particularly important to do the steps in the right order.. powering off, etc.. I suggest removing the card and seeing what happens. Then carefully reinstall the card making sure that it is securely inserted into its slot, etc.. You may want to check if it is all the way into its slot before doing anything else. It does take a fair amount of force to properly seat an Airport card.