Currently Being ModeratedFeb 24, 2013 3:26 AM (in response to fish1947)
What is the second HDMI display you are using ?
Have you selected the HDMI input in the menu set up on this second device?
Is Mirror, deselected in; Apple > system preferences > displays > arrangement
Have you tried rebooting the mac so that the second display is powered on and switched to HDMI before the Mac is powered on?
Have you tried using the HDMI adapter on another divce to test if it is functioning?