I am trying to hook my pc to the tv using a vga cable. When I press "input" in order to arrow down to select VGA, thehighlight bar will not move! I cannot select anything but TV. If I press video, comp or HDMI, then input in attempts to arrow from that position, it goes right back to TV. I have tried using all arrows, volume and channel. I have also tried using buttons on the side of the set. HELP!