I have had this problem for several versions now, that embedding objects does not work properly.
If I embed a Google Map, for example - I know from reading online that I must do this in the HTML editor. Switch to HTML editor, save draft, preview post and the map is there. Switch to Visual mode to continue editing, and it is still there.
However, add another Google Map in the same way - switch to HTML, add, back to visual, and the first map disappears. If I switch back the HTML viewer, some code remains, but it doesn't work.
Instead of seeing the map, I just get the link to "view larger".
YouTube video is similar. I'm typing a post, want to add a video with YouTube's embed code, so I go to HTML, paste in YouTube's video code, then go back to Visual to continue my post. The video is there, and visible. As soon as I switch to HTML view to add something else though, my earlier video disappears and is replaced by simply one nbsp in the HTML code.
In fact I've just discovered the point at which it disappears.
It's when I go back to the HTML view.
Visual->HTML is fine, when I add the code.
I can go back to Visual fine.
When I go back to HTML again, my embedded YouTube video code is gone.
Must I type the entire text first, then add all the videos, maps, etc. in HTML mode at once? That's not generally the way I work, as I'll come up with ideas half way through a post. Plus as I can't copy/paste from notepad into WordPress, without it misinterpreting all my line returns, I'm forced to write it directly into the editor.
What if I need to modify it at a later date? Can I never go to visual mode, if I might want to return to HTML again?
I'm sure this used to work flawlessly switching back and forth, but now it borks anything I've embedded.
I am using the Nature_wdl 1.3 theme, and have no plugins related to embedding or graphics/video viewing - just things for anti-spam, and mobile themes (WpTouch).
I have just logged into another WordPress install with a different theme, running WordPress 3.0.1 and I have the same problem.
Any help much appreciated.