Oh shit. The computer worked fine between 3 this afternoon and a little past six. Then I went to the kitchen to start a pasta sauce. And when I came back five minutes ago, I started getting the same message again: Safari can't establish a secure connection to the server. As before, System Preferences and the little fan icon tells me I'm connected.
Now what?
I've shut it down. Going to the kitchen to finish, and I'll try again when I come back.