Mine is the Roku add on unit. I have four of them and two do it and two don't. The easiest fix I've found is to pull the power plug out of the Roku unit and plug it back in and it works fine after that...for a while. Haven't found what sets it off, but I have noticed that if you hit the home button while its doing the no sound thing, you can still hear the tone for selecting something, just can't get any content volume on any service. It seems to me to be something to do with the way the Roku streams to the HDMI cable. Disconnecting the HDMI cable at the Roku unit will not fix the issue, only pulling the power cable at the Roku does. At least that fix doesn't require any additional work, just takes a few minutes for the Roku to find it's mommy and then everything works like normal.