You may have some interfernce between HDMI and aerial cables. Try to use better cables or put some distance between the two.

ANother possible option that I had in the past is that some channel transmit the video in a smaller area. In this case is up to the TV set to visualize correctly the image.

In my TV (KDL32W4000) in the set up menu - Screen setup there is an option called "Full pixel" ("Pixel pieno" in Italian) in which the TV is not changing anything (and so the accuracy is better) but you may encounter the problem that you have; if you set it up as "Normal", it should fill all your TV screen so cancelling the unuseful first pixel line.. let's try.

Hi Anthony,

I had a look at the i-manual of your tv and the option is under the display menu/Screen sub-menu

It applies only to external source so this is why you don't have problem with the internal decoder.

Have a look at the actual setting, if it is Full pixel switch it to normal