Gear:

All gear same age- sorry don't have exact model numbers at the moment:
Two rooms with same set up basically.

Samsung TV's couple years old or so - higher end models (with the exception of an 8000 series that is probably 5 years old)
Onkyo Receivers
Key Digital 4x4 matrix switches
Apple TV 3's
Xfinity X1 boxes
Oppo Bluray
All longer HDMI connections to TV's are Ethereal high end cables. The short 1 to 2 meter interconnects are Binary locking HDMI cables.

Both system run sources to matrix, then out of matrix to receiver, then on to the TV's.

Both areas serve two samsung TV's off their respective matrices, and are independent systems.

Both exhibit the same issue after having worked for at least 2 years:

Xfinity and Oppo work fine

The problem:

On both set ups, Apple TV will display when showing the screen saver, but the minute you hit "menu" or anything else to wake them up, the screen goes black - it looks like the TV's still show a signal detected, but it's just a black screen.

This happens with both or only one TV operating.

I believe I had auto update turned on in the Apple TV and Samsung (bad idea). I had the customer check on TV for Samsung update and it shows no update available. I haven't been there yet to check it out, but hoping MAYBE someone else has seen this issue???

Seems like it would have to be a rouge software update. The questions is how the hell to fix it quickly.

I've already done the whole reboot thing, including TV's.

Video through the matrices are going to the lowest common denominator - basic dumb switches.

Video processing should be turned off in the Onkyos - I hope.

What causes this on the HDMI end of things?

Not sure the answers to your questions, but Ive often eliminated ATV issues by changing the ATV to 720 from 1080 or auto. Cant tell the differnce 98% of the time anyway in pic quality.

Video Blanking = HDCP error usually.

Could be the resolution on the ATV is set to auto or 1080p while the other devices are set to 1080i.

So when you switch the handshake is renegotiated and it fails.

If it worked for 2 years and now is failing it is either - HDMI chip in that matrix is going or (what will probably be the issue) some setting in the ATV changed during a software update

+1

Bypass the onkyo's.

I have zero issues with any of my appleTV's in the field for the last 6,7-8 years at least. Only time I ever did was when I was using a SNAP Coax->HDMI Balun and had to goto 720p from 1080.

If his matrixes have optical audio, then he should be all set.

Potential Onkyo HDMI board failure... like they have in the past.
If dropping the resolution doesn't work, try a product that sorts out the clock stretching of the HDMI products.

Sounds like a known issue with the latest Samsung firmware, certainly in the EU anyway. Samsung are working on a fix, but the workaround is:

Settings, Broadcasting, Turn off Autotuning.

This seems to have resolved all my black screen issues.

Dupe...

Just re-read your OP, you issue does sound slightly different, but maybe related so probably worth a try. We are mainly seeing issues after the TV has been off for several hours and displays a black screen once turned back on.

I know this is of no help. Just a simple answer to the original question. HDMI is the cause of your issue. It should be sold with HDMI use warning of side effects similar to drugs. While HDMI may work, your integrator has determined the benefits of using HDMI out weight the potential negative side effects.........
You get the idea. Only difference is a doctor gets to prescribe a different drug and say see you in two weeks with another bill. And the HDMI people keep getting their share of the pyramid profits because of that little name on the cable somewhere.

Common side effects of HDMI include: infection, ataxia, blurred vision, constipation, diplopia, dizziness, drowsiness, fatigue, headache, peripheral edema, tremor, weight gain, visual field loss, accidental injury, and xerostomia. Other side effects include: abnormal gait, abnormality in thinking, amnesia, arthralgia, asthenia, cognitive dysfunction, confusion, edema, neuropathy, sinusitis, speech disturbance, vertigo, visual disturbance, myasthenia, amblyopia, increased appetite, and twitching. See below for a comprehensive list of adverse effects.

[Link: support.apple.com]

Also stop using onkyo and pioneer. I was recently plagued with these issues. Switched to my normal go to Denon. No probs.

Are your AppleTVs set to RGB high in the video output settings? They can get wonky when going through a matrix. Fixed the issue for me.

I have a GREAT new business plan. It's called HDMI Insurance Inc. The premiums are kind of high though.