Embedded videos disappearing

Hi,

I’m wondering if anyone can solve this puzzle?

When I copy and paste the embed code of a youtube video into the html screen it doesn’t always show up on the finished page. It just leaves a blank space.

At other times I have had it appear ok put some text between the videos (usually by going back to Visual to add the text) and have it stay there. Only to have the videos disappear again once I have put some bullet points in the text.

Any ideas?

Thanks
Darag