In the wysiwyg editor for a post there is a button "insert media". If you click this, you can post a youtube video by pasting in the one line code found on Youtube in the "share this" section - NOT the code found in the "embed" option.
Example of "share this" code:
[media]
Example of "share this" code:
Code:
http://www.youtube.com/watch?v=-l4L--SJ6DA
[media]