I was out in the garden shooting with the A7r that I picked up a week and a half ago and the EVF and screen went totally black? Couldn't get the menu, or, anything else to come up. Changed batteries, put a different SD card in, and sacrificed a chicken, but, nothing.
At my camera store, they tried (without the chicken) to get it going. Nothing (although that's usually when the problem that you were having doesn't evidence itself). They hadn't seen anything like this before. Gave me a new one and they're sending that one back to Sony.
BTW: it was still taking pictures when the screen was black.
Anybody had any problems like this with their A7/A7r?