TV Blacks out; Mode not supported message on TV screen.

One TV was intermittently blacking out.  Sometimes I would get a screen message saying "Mode not supported".  It was driving us nuts.  I replaced the cable box 4 times, swapping tvs with another room, talking with technical support and having 1 service call confirming my signal to the house was very good without a resolution.  Then it finally hit me.  What haven't I switched out?  The HDMI cable that was supplied by Xfinity.  I went to the orange box store and bought a "deluxe" cable; not the basic one.  EUREKA.  Problem solved.  After 4 days, no blackouts or messages.

If you are having similar issues, try my solution.  You can always return the new cable.