I had a similar problem when I added my 2nd 5770 in April. The option for crossfire did not appear until I did a complete uninstall/reinstall of CCC. The latest version out right now is 11.6 - make sure you get that. Upon rebooting after the reinstall a window will pop up and say that crossfire is detected and confirm that you want to enable it. Make sure your crossfire bridge cable is attached as well. Good luck!