Mozilla Plugin crash at appendChild

When I dynamically, programmatically create an embed with VLC, the Plugin !sometimes!, not always crashes when I try to add it to a body Element (in a Frame) with appendChild. This happens in about 1 of 3 trys in Mozilla Firefox 5 and Google Chrome. I haven't tested it with safari or anything else yet, because if Firefox and Chrome doesn't work, I need to work on with version 1.0.9 (this problem is since 1.1.11). I got no problem in IE.

This is the JS-Code with which I try to add it:

vlc = top.miraMenu.document.createElement("embed");
vlc.setAttribute("id", "vlc");
vlc.setAttribute("type", "application/x-vlc-plugin");
vlc.setAttribute("pluginspace", "http://www.videolan.org");
vlc.setAttribute("version", "VideoLAN.VLCPlugin.2");
vlc.setAttribute("width", 1);
vlc.setAttribute("height", 1);
top.miraMenu.document.getElementById("overscan").appendChild(vlc);

at the last line it crashes sometimes (thats what firebug says when I debug it)

The HTML Structure looks like this:

<html>
  <frameset>
    <frame />
    <frameset>
      <frame />
      <frame id="miraMenu">
        <html>
          <body id="overscan">
            <div />
            <div />
            <div />
            <div />
            <div />
            <div />
            <!-- Here I want the embed -->
          </body>
        </html>
      </frame>
      <frame />
      <frame />
      <frame />
      <frame />
      <frame />
      <frame />
      <frame />
    </frameset>
    <frame />
  </frameset>
</html>

I work on a IPTV Software and need to refresh Data while showing some other things, thats why I need that much frames to be able to work as if I have Threads.

Best regards

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