I upgraded AucTeX to 12.1.2, hoping that it would fix a problem with the displaying of verbatim environments.
This caused a range of problems which I am trying to track down step by step.
One is that the Preview, LaTeX and Command menus disappeared. Instead, I now have a "TeX" menu right of "Tools". The mode displayed in the status bar is "LaTeX", though.
This seems wrong to me. There are more things that are broken, but I'd like to start with that.