             
             // TODO: Need to force the contentGroup to removeChild on its content children
             // before the any other Group adds the content children
-            contentGroup.content = null;
+            contentGroup.mxmlContent = null;
             contentGroup.validateProperties();
         }
     }

            {
                _placeHolderGroup = new Group();
                 
                if (_content)
                    _placeHolderGroup.content = _content;
                
                _placeHolderGroup.addEventListener(
                    ItemExistenceChangedEvent.ITEM_ADD, contentGroup_itemAddedHandler);

                }
                
            }
            else if (_mxml_content != null)
            {
                contentGroup.mxmlContent = _mxml_content;
            }
            
            // copy proxied values from contentGroupProperties (if set) to contentGroup
