LoadUnityWeb() can only be used once per session?

I am trying to create preloader that I can hand to game portals, which loads a "shell" that queries php to find latest game version, and then in turn calls another LoadUnityWeb() on the URL of the latest game version.

Has anyone else had trouble loading in a unity3d file using LoadUnityWeb(), and then from within that new unity file calling yet another LoadUnityWeb() ?

I get "fatal content error"'s, and Unity crashes completely once the second LoadUnityWeb() is called.

     function Start () {
         // Start streaming the data file
         var stream =
           new WWW ("http://www.unity3d.com/webplayers/Lightning/lightning.unity3d");
         // Yield until stream is done
         yield stream;
         // Load it!
         stream.LoadUnityWeb();
     }
     // Streams a .unity3d file and displays the progress in a GUI texture.
     // You need to make sure the GUI texture is set up to have a pixel inset.
     function Start () {
         // Store the original pixel inset
         // and modify it from there.
         var originalPixelRect = guiTexture.pixelInset;
     
         // Update the progress bar by scaling the gui texture
         // until we reach the end
         var stream =
           new WWW ("http://www.unity3d.com/webplayers/Lightning/lightning.unity3d");
         while (!stream.isDone) {
             guiTexture.pixelInset.xMax = originalPixelRect.xMin
                   + stream.progress * originalPixelRect.width;
     
             yield;
         }
         // Update it one last time before loading
         guiTexture.pixelInset.xMax = originalPixelRect.xMax;
     
         stream.LoadUnityWeb();
     }