I've a problem with HDMI on my ultrabook. One week ago it worked fine but now there is a problem. When I connect it, Ubuntu recognize the monitor-tv but it's black/blank, no image will display. Someone can help me? Thanks
Ok, let's try and see if Ubuntu knows the second monitor.
Open the Dash and type "Display". Enter the program and you should see 2 monitors there, one your laptop and the other your monitor connected trough HDMI.