Problem solved!  We had an AT&T tech come by to check the system.  He found that our system was so old that he had to replace almost everything.  We were among the very first Uverse customers and much has changed, it seems.  The 'filter' was the first thing he checked, and he said he was surprised we could get any signal at all because this 'filter' could not keep up with the current signal rate.  Then he discovered that the original AT&T installer had used the old Roadrunner/Comcast lines and connections, which are not compatible with the current Uverse signal, so he changed all of those.  Then he found that the router was out of date, so he changed that.  After everything was changed except the DVR, life is good.  Everything works again.  Have not had a frozen screen or the blue screen of death since everything was updated two weeks ago.  Hats off to Steve and his professionalism.