I_am_so_embarrassed. Your suggestion fixed Task Manager. How/why in the heck would that have happened!? The only way I did that was through a series of accidental clicks by my cat.
If you're tracking, my search for this problem was: "task manager not updating" led me to verifying corrupt files, which led me to DISM, etc, which led me to Windows updates not working right, which led me here.
As far as ESET not working, I want to figure that out too. Is there another AV you would recommend in the interim?