I've been so busy this week that I only just now got a chance to install this update. Although it's a small one, something in it seems to have fixed all the mysterious problems I had with hibernating and Bluetooth last week.
I've only installed it on my main laptop so far, but I'm hopeful. I updated, started 10 or so applications on their virtual desktops, and then hibernated. When I woke up the laptop, everything was exactly as it should be. And there were no issues with Bluetooth, either.
So, a lot of crap fixed, apparently, and I've given up my plans to do a system re-installation out of desperation. Hoping that the rest of my upgrades work as well! Later ...