Same problem
I am having the same problem with my VSX-823-K. My problems just started yesterday 2/19/16 and my receiver is less than 2 years old also.
I turned the unit off and a couple of hours later turned it back on to watch TV and PooF no picture or sound to the TV or Receivers Speakers and not able to get sound when playing a CD on my BD player. Can still stream music from AirPlay on my PC but with no TV display. Verified it is not the TV, Cables, etc. Seems like a bad HDMI board as radio works, AirPlay works, only devices that use HDMI are non-functional. Really getting tired of all these HDMI problems with A/V equipment as I bought this unit to replace my Onkyo receiver that had a bad HDMI board and failed after two years. Good news is I found where Onkyo is now repairing those receivers and have ordered a box and shipping label from them.
I would call Pioneer Support except that I've talked to them before and they are worthless. Of course this unit is out of it's one year warranty and at one time, about a year ago I had a problem with this unit independently adjusting it's volume down and flash "TEMP" on the display. At the time it was barely in warranty and sent it in but they could not duplicate the issue and sent it back saying it was fine and it didn't do that again for about 6 months then started again if volume is turned up to loud. I have been buying Pioneer receivers since the late '70's, but this one is a piece of junk and has been from day one and I wouldn't ever buy anything made by Pioneer again!
The only thing left to try is a restore to factory default on the receiver and I hold no hope for that helping the situation at all, as that has never helped problems in the past with the unit. UGH.
What result did you finally have with your unit doing the same thing?