OS X Mountain Lion: Join a Wi-Fi network that is protected with Wi-Fi Protected Access

Network Diagnostics determined that the Wi-Fi network you want to join is protected with a Wi-Fi Protected Access (WPA) password.

You need to enter the password exactly as it was given to you by the network administrator.

WPA-protected networks often require that your MAC address be registered on an authentication server.

If you still have problems joining the WPA network after entering the password, check with the network administrator.