Flash detection code not working in IE

I've moved the flash detection script that is generated by Flash MX into a function and then called this function onLoad. I've tested the code with several alert boxes. In Internet Explorer the line "var plugin = (navigator.mimeTypes && navigator.mimeTypes["application/x-shockwave-flash"]) ? navigator.mimeTypes["application/x-shockwave-flash"].enabledPlugin : 0;" returns 0, this used to work when not in a function. This works fine in Mozilla 1.4

The code:

<script language="Javascript1.1">
<!--
function write_flash(srcFlash, srcStatic, fshHeight, fshWidth, mapName, loop)
{
      var MM_contentVersion = 6;
      var plugin = (navigator.mimeTypes && navigator.mimeTypes["application/x-shockwave-flash"]) ? navigator.mimeTypes["application/x-shockwave-flash"].enabledPlugin : 0;

      if (plugin) {
            var words = navigator.plugins["Shockwave Flash"].description.split(" ");
            for (var i = 0; i < words.length; ++i) {
                  if (isNaN(parseInt(words[i])))
                        continue;
                  var MM_PluginVersion = words[i];
            }
            var MM_FlashCanPlay = MM_PluginVersion >= MM_contentVersion;
      } else if ((navigator.userAgent && navigator.userAgent.indexOf("MSIE") >= 0) && (navigator.appVersion.indexOf("Win") != -1)) {
            document.write('<scr' + 'ipt language="VBScript"\>');
            document.write('on error resume next\n');
            document.write('MM_FlashCanPlay = (IsObject(CreateObject("ShockwaveFlash.ShockwaveFlash." & MM_contentVersion)))');
            document.write('</scr' + 'ipt\>');
      }

      if (loop == true) {
            loopParam = '<param name="loop" value="true">';
            loopCode = '';
      } else {
            loopParam = '<param name="loop" value="false">';
            loopCode = 'loop="false"';
      }

      if (MM_FlashCanPlay) {
            document.write('<object classid="clsid:D27CDB6E-AE6D-11cf-96B8-444553540000"');
            document.write(' codebase="http://download.macromedia.com/pub/shockwave/cabs/flash/swflash.cab#version=6,0,0,0"');
            document.write(' id="'+mapName+'" width="'+fshWidth+'" height="'+fshHeight+'">');
            document.write('<param name="movie" value="'+srcFlash+'"><param name="menu" value="false"><param name="quality" value="best">');
            document.write('<param name="scale" value="noscale"><param name="bgcolor" value="#000000">'+loopParam);
            document.write('<embed src="'+srcFlash+'" menu="false" quality="best"'+loopCode+' scale="noscale" bgcolor=#000000 ');
            document.write(' swLiveConnect="false" width="'+fshWidth+'" height="'+fshHeight+'" name="'+mapName+'"');
            document.write(' type="application/x-shockwave-flash" pluginspage="http://www.macromedia.com/go/getflashplayer">');
            document.write('</embed>');
            document.write('</object>');
      } else {
            document.write('<img src="'+srcStatic+'" width="'+fshWidth+'" height="'+fshHeight+'" usemap="#'+mapName+'" border="0">');
      }
}
//-->
</script>

further down the page I call the function with:

<map name="eyes"></map><script language="JavaScript1.1">document.onLoad = write_flash("_flash/eyes.swf", "_images/kmx_eyes.jpg", "91", "203", "eyes", true)</script><noscript><img src="_images/kmx_eyes.jpg" width="203" height="91" usemap="#eyes" border="0"></noscript>

This is weird as all I did was move it inside a function, first without any modification, and it stopped working. I modified it later thinking I could work the problem out but for some reason the "var plugin =..." is not working now in IE.

Any help appreciated. Sorry about the points on this question I've only just registered, will have to earn a few ;)