This started to happen just a few days ago. I think it happens mainly, maybe only, if I copy a link or something else that comes underlined from the web. When I try to return to ordinary writing in my message I simply can't do it. The underline button goes 'off', but the underlining continues. I tried flicking that button on and off a few times, no help. I tried moving way down on the page to start the new text, no help. Flummoxed.