I'm sorry, John. I had sent a reply earlier but it looks like it didn't go through.
In short, there really isn't anything you can do in this situation, other than a microprocessor reset (restoring factory default settings, clearing the memory), and updating the firmware if it isn't on the latest version.
In every case of this same situation I've seen, it always comes down to a hardware fault, meaning a bad digital pcb, which is the control board that contains the hdmi circuitry. The hdmi components (in all devices, not just this receiver) are highly sensitive and are easily damaged by power surges and even fried by static shock just from your body touching it or connecting/disconnecting devices while they are powered. This is not a simple fix, and not even something that can be repaired at the component level. The parts aren't even available in the first place, but even if they were we are talking about integrated circuits here that are beyond the soldering skills of most. Yamaha does not make these boards available to the public either, it would have to go to a factory authorized service center, and even in that case is not worth fixing. This is a 2007 model, so it is already years past its service life, and the cost of the part alone, if the board is even still stocked, will be over $400, + labor costs. It just isn't practical when you could buy a brand new and updated model that can handle networking, 4k, 3d, etc for less than you'd spend even on parts for this one.
I can help you through the reset/update process if you'd like to try, or I can help find a repair shop or recommend replacements.
Alternately, what I'd suggest is bypassing the receiver for video - there is no net gain to routing video through it anyway as it doesn't upscale or do anything else for you. Just hook the hdmi devices directly to your tv/display and run an optical cable from the tv back to the yamaha for sound, so you can keep using it as-is.
Best regards, ***** ***** for the news,
I am an independent technician and I've spent my personal time, unpaid, in an effort to assist with the question for which you solicited my services. This site works on the honor system, and to that end, I have prioritized working with you ahead of other paying customers.
I am only paid for my efforts when customers such as yourself leave positive feedback for my work. Again I apologize there is not a better outcome here, though this is really beyond either of our control. I do hope you’ll consider leaving a positive rating for me, rather than “shoot the messenger”, so that I may get credit for my time spent in good faith to answer your question accurately.