I just created a post which includes images and two embedded youtube videos (I have done this before with no problem). Everything looked fine, but I noticed a typo, so I went back to the post and edited the word. When I went back to the live post (after clicking update) the typo was fixed but the videos were gone. I thought maybe I had somehow typed over them. So I went back to youtube, got the embed code and re-added them to the post. Worked fine, everything was there. I wanted to make sure everything was working properly so I simply added a second period after the first sentence and tried a "Preview" - the videos were again gone. I didn't save and then I closed WordPress. I then re-opened WordPress and tried the same test (with the extra period) and again the videos disappeared.
Can anyone help?