Before today, I'd used the word processor editor plenty of times. I don't know what happened to break it. This morning I received this error message and then found the article linked above.
I initially tried option 3, but when I tried to install the downloaded file, it canceled the installation saying it was already installed. I tried option 2, but didn't find the file that it referred to and anyway it probably would have said the same thing.
My solution in Windows 10 was to go to add and remove programs, find DHTML, click to modify the installation, then repair the installation. I first did this process while Microstation was open; I wasn't surprised when it didn't work while I was still in the same session, so I closed Microstation. Because I didn't want to waste too much time, I decided to run the repair once more while Microstation was closed. When I started Microstation again it was fine.