Using Avid HD I/O-HDXcard and Hync HD

Can’t seem to get cubase to allow me to choose Avid HDX in my ASIO connections. No connection is checked and gives the option for Avid HDX but doesn’t change when I select it. I was told the Avid hardware would work but I can’t get to work. Running a power mac osx 10.8.2 which also has protools 10 installed. Help anyone? :confused: