Javascript addEventListener onStateChange not working in IE

IE doesn't support addEventListener does it?? You need attachEvent right?

if (el.addEventListener){   
    el.addEventListener('click', modifyText, false);    
else if (el.attachEvent){   
    el.attachEvent('onclick', modifyText);   
}

from testing in IE it looks like the reference you are using

ytswf = document.getElementById('ytplayer1');

is assigned before the actual swf object is loaded, so IE thinks you are referring to a simple div element

you need to run this code

function onYouTubePlayerReady(playerId) {
  ytswf = document.getElementById("ytplayer1");
  ytplayer.addEventListener("onStateChange", "onytplayerStateChange");
}

right after you call

swfobject.embedSWF("http://www.youtube.com/v/SPWU-EiulRY?
hl=en_US&hd=0&rel=0&fs=1&autoplay=1&enablejsapi=1&playerapiid=ytvideo1",
"popupVideoContainer1", "853", "505", "8", null, null, params, atts);

before you close out that $(function()

and place var ytswf; right after the <script> instead of further down