Go into the video control panel after hooking up the laptop to the HDTV and look for an option to make the HDTV an extended desktop or clone the laptops's desktop.
Assuming you are simply using the Intel HD graphics core:
http/www.intel.com/support/graphics/sb/cs-031023.htm
If you are getting an error after performing the above, then...
Try connecting the laptop to another HDMI port on the HDTV (if there is one).
Connect the laptop to a monitor to see if you get the same result.
Try a different HDMI cable.