Hi Dan,
You only need to use one of the tags ( <video:player_loc>or</video:player_loc>
<video:content_loc>).</video:content_loc>
This is what I'd use:
<video:player_loc allow_embed="yes" autoplay="ap=1">http://player.vimeo.com/video/24580638</video:player_loc>
Davinia