NATIVE RESOLUTION of your TV?

Unless I am wrong it is a 720p format so the native resolution is 1280x720 pixels which should eliminate your artifacts. Most computer monitors are higher-resolution than even the
highest-resolution TVs, meaning you lose resolution quality and working
room. Consider this before using a TV as a computer monitor. If you want more on the screen graduate to a 10801 or 1080p TV which will have a resolution of 1920x1080 pixels at 60 Hertz

Try this for guidance:
http://www.ehow.com/how_5760731_use-720p-tv-monitor.html