The TV is Samsung LED 1080p from about 10 years ago; don't remember the brand of the HDMI switcher. The other cable box, apple tv and blu ray work fine with the same TV and switcher. The only other thing I haven't tried yet is swapping the HDMI inputs of the two cable boxes just to rule out a bad HDMI input on the matrix. It just doesn't look like an HDMI issue; the problems that I've seen in the past would affect the entire screen(sparkles, green screen, flickering etc). This feels like an internal issue with the cable box since only the bottom of the screen is affected.