I had the same errors. I changed the stop() to fix them.
Normal function: StopVideo();
The "clean" code:
<a id="stop" href="#">Stop</a>
<iframe id="popup-youtube-player" width="640" height="360" src="http://www.youtube.com/embed/geTgZcHrXTc?enablejsapi=1&version=3&playerapiid=ytplayer" frameborder="0" allowfullscreen="true" allowscriptaccess="always"></iframe>
$('#stop').on('click', function() {
//$('#popup-youtube-player').stopVideo();
$('#popup-youtube-player')[0].contentWindow.postMessage('{"event":"command","func":"' + 'stopVideo' + '","args":""}', '*');
});
http://jsfiddle.net/3J2wT/266/
I hope it will be help you.