Welp, I'm 95% sure it's the cable. I could run one more test to make sure, but that would mean unplugging one of my HDMI cables from the back of my receiver from my DVD player, or PS3, and taking it back upstairs to the first TV and testing that cable up there. But they're all zip tied together and that would be a pain.
The cable in question is a pretty cheap one I got from Amazon some time ago, is that dumb? I've read a lot of different places that HDMI is HDMI, and I definitely am not going to buy the diamond one for $10K, but does anyone have any suggestions for cheap HDMI cables that won't shit out after a year? This cable has actually acted weird on us pretty much as long as we've had it, so it's not surprising that it's taken a shit on us finally.
I know the question has been asked and answered a hundred times, but thanks for any suggestions.