Don't have a HDTV but have an HD box,
Last night all channels played in standard definition (full screen), this morning seemed fine as well.
Afternoon half the channels were playing with the widescreen black bar thing at top and bottom.
Can't stand that setting and wondering how to change it back. Nothing in any of the manuals about it
Checked other tvs in the house with standard digital cable box and they have the same problem.