…thanks to Camera Tech of Anaheim (1347 S Anaheim Blvd, Anaheim, CA 92805; just south of Ball). $95 out the door. As I'd suspected, a connection between the main circuit boards and the card reader had failed.
I'd recommend this place. Sole proprietor, and an Englishman to boot; he's a Londoner, been here 30 years. The tiny shop is full of ancient and modern cameras. Behind the counter are piles and piles of cameras and bits of cameras.
Despite being an old-school camera guy, he's also au fait with digital technology, and has a bunch of old digitals for sale, immaculately CLA'd and in nice shape indeed. When I was there the first time, he was espousing the quality of a Sony F717, and the second time, he was taking in a flash to repair from a wedding photographer. Seems to know his stuff, and there are a bunch of online reviews that like him as well.