Aaaand they weren't able to find anything. It's being escalated to a local tech who will probably send me a new laptop.
@tyghebright unless your laptop is entirely absent things that spin, you could have a chip vibrate out just a wee bit. Also... gremlins can cause RAM to just be Not Good suddenly. Usually, though, it's Windows that breaks it ;)
OK, just spent 45 minutes online with tech support... and we've determined that it's a hardware issue. She think's it's the RAM. (I don't know why that would suddenly be an issue when I've had the computer for a year.
Tomorrow morning, she'll call me back and we're opening her up.