The visual editor started working again on my computer; no explanation of why it didn't for a while. If there was some problem with it that prevented it from working for the last week or so, it would have been nice to get an error message, so that I would know why it disappeared.
Previously, when I clicked on "edit" for a page in a wiki I started (in February), a visual editor came up, with the source editor as an option. Now, only the source editor comes up; I've looked all over for an explanation, but haven't found one. I didn't change any preferences, and it is the same on some other wikis I looked at. Does anyone know why?