Why am I losing all scene data when loading an Asset Bundle-loaded scene?

I'm working a Unity iOS pro project where we make use of asset bundles. I dynamically download the asset bundle which defines an entire scene. I currently use the following procedures to load in an asset bundled scene which seemed to work in Unity 3.5.1, but doesn't work for me anymore (I get a completely empty scene) after I upgraded to Unity 3.5.2:

     public IEnumerator DownloadLevelBundle(int levelId, int versionNumber = 1)
     {
         WWW download;
        
         string downloadUrl = ...; //omitted
         Debug.Log("About to download " + downloadUrl + " ...");
         //download = new WWW (downloadUrl);
         download = WWW.LoadFromCacheOrDownload (downloadUrl, versionNumber);
        
        
         yield return download;
        
         if(download.error != null)
         {
             Debug.Log(download.error);
             return false;
         }
        
         Debug.Log("Level downloaded");
        
         AssetBundle assetBundle = download.assetBundle;
        
         if (assetBundle != null)
         {
             Application.LoadLevel("main"); // the scene file is called 'main'
             Debug.Log("Waiting for end of frame...");
             yield return new WaitForEndOfFrame();
         Debug.Log("Frame ended");
             assetBundle.Unload(false); // only free the scene after the frame has ended
         }
         else
             Debug.Log("Couldnt load resource");
     }

When I had previously encountered this issue, I figured it was due to the fact that Application.LoadLevel defers loading the objects until the next frame, hence I added in the frame yield. This no longer does the trick though.

Oddly enough, if I do TWO next frame yields, all my scene data appears, but the entire Unity IDE crashes when I stop playing.

Any ideas of what I need to do to a) get the scene to appear, and b) not have Unity IDE crash when I stop playing the scene?

Thanks in advance, Jason