Apple’s original AirPort card appears to be physically incapable of WPA/WPA2 encryption. The software doesn’t tell you, of course — it just silently fails to work.

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WPA will work on the original AirPort Card. You need to be running 10.3.9 Panther and the AirPort 3.3.1 software update (AirPort 3.3.1 is not a combo updater, 3.3 is. You need to upgrade to AirPort 3.3 then install 3.3.1).

AirPort Card: When You Can Join a WPA Network