This morning I was suddenly unable to change channels/access the guide on the cable box in the living room ... When I change channels or make inputs on the cable box itself it responds instantly ... I can use the [living room] remote ... in other rooms ... I switched cable boxes and ... the box I moved into the living room has the same problems ... In summary, multiple boxes and remotes having communications issues in just one room ...
There is clearly some interference between a device in the living room (probably the TV, but then maybe not), and the STB/remote control combination in the same room.
You have not provided sufficient detail to go much further. For example, what are the model number of the various STBs, what are the types of display devices involved, is there additional equipment in the living room that also has IR capability and uses another remote, what are the actual arrangements of equipment from room to room (this may affect interference issues)?
It is a known problem that certain display devices interfere with the IR control mechanism used by the remote control and the STB in question. Let us know more detail, and we'll go from there.