Be sure to scroll down this string. If you have Xfinity boxes through Comcast, there's a good chance all you have to do is push the reset button on your cable box. After running through all the reset options for the TV and its various display settings, I read Ray Negron's post. He suggeste a VERY simple fix that worked great for me. Just hold the reset button on your Xfinity box until the blue power light goes off. Wait 20 seconds and repower the device by pressing the reset button again. Shadow across top of set disappears.