The problem I've been having with YouTube videos has been solved, or so it would appear. A TypePad technician asked me (by e-mail) whether I use the Rich Text editor to post videos. I do; but I always have, and until the other day, it always worked. I tried posting a video with the HTML editor. Voila! TypePad must have changed something, but I don't mind, since, now that I know the trick, I can work around it. I simply have to remember to use the HTML editor from now on. Thanks to everyone who made suggestions.