Green line at edge of screen

I have a Panasonic TH-42PZ77U hooked up via HDMI to a cogeco box.

I have not had any problem for the last 6 months, but in the last day or two I see an approx 1/2-1 inch green line on the far right of the screen this is only on the HD channels when in the normal mode if I switch to hd fill it goes away, but the picture sucks.

Any thoughts on what it could be? HDMI cable? Cable box? TV? Thanks in advance