Add us to the list of people experiencing this problem. We bought the cable to try and repair this ourselves as well as calling apple care ... twice. We live over 2 hours from an apple store. No matter which way you slice it, this leaves us out of luck.
Apple care told us this is a wide spread problem being caused by the update. Clearly not user error. Of interest they only told us this on our second call, after we invested the time and money to try and fix it ouselves.
We've only owned this apple tv for a few months.
We've been a family of die hard apple fans and are starting to lose faith. Apple doesn't seem to have the same commitement to quality products and superior customer care it once had. 😟
Perhaps it's time to go back to cable.