This is with Excel 2000. The other Alt and letter combinations work, with
File menu, Insert menu etc but for some reason when I press Alt E it only
causes a rectangle to appear around the word Edit, but doesn't open the drop
down menu.

Does this suggest Alt E has somehow been associated with another command?
How could I check this? Or is there any other explanation?

For years I have been subconsciously pressing alt E S V to paste values into
cells and it's very disconcerting when this no longer works.

Grateful for advice