Recently I had a bit of a problem with embedding videos in my newly-updated WordPress blog (not this one). It was WordPress 2.3 which so far has not caused any major issues that I am aware of in my own work.
The writer input all his text into the textarea, which included a reference to a video, embedded using the usual tags and so on. When he saved/published the post it caused a major snaffoo. For some reason it converted the characters, so a < became < and so on. It looked like some kind of Martian dialect.
Thanks to Robert who called me (Robert, comment to this post so I can link to you please!) he pointed out the cause of this issue. In the case of the writer in question the rich text editor was set to be on. Apparently, turn it off (Admin Panel -> Users -> User in question), repost and the issue disappears. Robert, he’s trying that so I’ll post an update to this post.