The Wide Fit feature requires one of the following before it can enable:

DTV = 1080i signal
Component = 1080i, 1080p
HDMI = 720p, 1080i, 1080p

You might want to make sure your cable box is outputting one of these specific signals based on the connection and the box's internal menu.

Wide Fit will not work on ATV, S-video inputs, Component at 480i/p, or through the PC inputs.