unplug it for a minute or so. Not just turn off with the remote, completely unplug it from the outlet. If you have modified the sound settings in any way, you might try resetting to factory defaults. My problem occurred when I adjusted the audio and video settings and this particular TV apparently didn't like it. After the unplug and full reset, there were no more problems. I also could no longer mess with the audio and video settings. It sounds like your problem is more Xfinity related, but hard to say really. Best of luck.