I’m not quite sure how in the world this happened, but the following keys stopped working for me:
Backspace
Enter
Arrows
Home/End/Page Up/Down
Clicking or highlighting with the mouse
mouse scroll wheel
Hotkeys with control (e.g., I can’t get to the find-anything menu with ctrl-p, but if I go to the menu I can get it to show up. And enter will dismiss that.)
Other programs seem completely unaffected. I’m at a loss as to how I got into this situation or what to do to fix it.