Macbook core duo, just lost airport!

[bored911]

so i have been in and out of the apple store for the last 3 weeks, and they have replace EVERY single part in my laptop, unable to find why it was freezing. Well this time they decided to replace the logic board for the second time and the airport card. I got it back, and they seemed to have fixed the freezing but now i can't connect to the internet via airport. I looked in "about this mac" and system profiler but it turns out that my comp thinks that there is no airport card. The weird thing is that it was working for about half and hour, then i tried to click a link on wikipedia, realized that my airport was dead, restarted, and now my airport symbol is gone from the menubar. Does anyone know what to do without going back to apple so they can waste more of my time