Hello, this is my first thread so I am sorry if I am doing something wrong.

When i plug in my hdtv with hdmi cable and enable Dual-monitor via catalyst control center, ubuntu gets all laggy and uncomfortable, if the hdtv is unplugged everything runs smooth and nice.
my question is what can I do to make it as smooth as when I only have my primary display enabled, I have searched google for hours and hours and have not found a thing that can help me.

I have a fresh copy of Ubuntu 12.04LTS