I fixed the YouTube for you. Embed code doesn't work here because we have to turn HTML on and that makes a vulnerable to hacks.
To get a You Tube video to play in the forum, treat it like a picture. Just take the http link to the video ( this one is http://www.youtube.com/watch?v=d4bJsIogkGk
) and wrap it with the "YT" tags. So.... [YT] [/YT] with the link inside of them. It needs to be on it'* own line and make sure you use capital letters. YT, not yt.