                 
                 thumbnailGroup = new Group();
                 thumbnailGroup.addElement(bitmapImage);
-                addChild(thumbnailGroup);
             }
             else
             {
                 bitmapImage = thumbnailGroup.getElementAt(0) as BitmapImage;
             }
             
+            // if thumbnailGroup isn't on the display list, then add it.
+            if (!this.contains(thumbnailGroup))
+                addChild(thumbnailGroup);
+            
             bitmapImage.source = thumbnailSource;
+            invalidateSize();
+        }
+        else
+        {
+            if (thumbnailGroup)
+            {
+                // null out the source and remove the thumbnail group
+                bitmapImage = thumbnailGroup.getElementAt(0) as BitmapImage;
+                if (bitmapImage)
+                    bitmapImage.source = null;
+                if (this.contains(thumbnailGroup))
+                    removeChild(thumbnailGroup);
+                invalidateSize();
+            }
         }
     }
     

    
    [Inspectable(Category="General", defaultValue="0")]
    [Bindable("durationChange")]
    
    /**
     *  Duration of the video's playback, in seconds

        videoPlayer.addEventListener(AudioEvent.MUTED_CHANGE, videoPlayer_mutedChangeHandler);
        
        // public events
        videoPlayer.addEventListener(MediaPlayerStateChangeEvent.MEDIA_PLAYER_STATE_CHANGE, videoPlayer_mediaPlayerStateChangeHandler);
        videoPlayer.addEventListener(TimeEvent.CURRENT_TIME_CHANGE, dispatchEvent);
        videoPlayer.addEventListener(LoadEvent.BYTES_LOADED_CHANGE, dispatchEvent);
        videoPlayer.addEventListener(TimeEvent.DURATION_CHANGE, dispatchEvent);
