     override mx_internal function getHeaderInfoAt(colIndex:int):AdvancedDataGridHeaderInfo
     {
         if(columnGrouping)
-            return columnsToInfo[itemToUID(columns[colIndex])];
+            return columnsToInfo[itemToUID(_columns[colIndex])];
         else
             return super.getHeaderInfoAt(colIndex);
     }

                    {
                        var sequenceNumber:int;
                        var descending:Boolean;
                        var sortInfo:SortInfo = getFieldSortInfo(columns[colNum]);
                        if (sortInfo)
                        {
                            sequenceNumber = sortInfo.sequenceNumber;

        }
        else if(!columnGrouping && headerIndex != -1)
        {
            selectedHeaderInfo = getHeaderInfo(_columns[headerIndex]);
            selectColumnHeader(headerIndex);
        }
    }
