title: refresh / reload a datagrid in flex
body: <p>I am using a datagrid. It has itemEditor components, combo boxes, etc. as aprt of columns.
  Ideally datagrid.invalidateList() method works to reload the datagrid with new dataProvider data.</p>
  
  <p>But, for me it is appending to the old data and new data gets added below the older data. I am not able to fix this reload of datagrid.</p>