Here is an additional observation that "feels" like the same issue:
I was adding an orthogonal line to and existing line.
The lineorthogonal command appears in the comand window, but the prompts to "select line" do not appear and the menubar (left of work area) does not switch context to the display of "where on the line to put it" e.g. grid, on-entity, endpoint, etc ( I forget the proper terminology).
As before, the "where to put it" is in Auto mode and the orthogonal line does place properly.