After many years of using TB without any problems on an older computer with Win 10 I suddenly have this confusing little hiccup. If I hit New Message, Reply or Forward a small rectangular box (about 8 x 100mm) appears with a shaded outline in the centre of the screen where the body of the email would go. There is also a black lock with a red line through it at the start of the "Subject" line of the blank email, I don't think I have seen it there before but I maybe wrong. Clicking inside the box gives nil response except on the far right on the formerly black X that has changed to a white X with a red background when it just deletes the whole page. No amount of right or left clicking outside the box gives any response except for the "error ding sound" and the box jiggles. The box can be dragged to the edge of the screen without any change in responses. All other email functions work normally, there are no problems with receiving, reading or deleting emails. I do not know how to find out what version of TB that I have installed. So to sum up if I hit New Message, Reply or Forward the only thing TB will let me do is delete the new blank email that I want to send (once it is completed). I have not got the foggiest idea of what to do to fix the problem.