Vending Machine-less Lounge:: AirPort Does Not Connect Automatically
If the above metod does not work, it is highly likely that your keychain searchlist is corrupt. You'll need to make sure that all three system level keychains
(System.keychain, X509Anchors, X509Certs) are in the searchlist /Library/Preferences/com.apple.security.plist. This file is an XML file, pretty easy to read. If one of the keychain is missing, go ahead and cut & paste another keychain's entry (from dict to /dict) and just change the index number and path.