jQuery Grid Plugin - jqGrid

I have a DataGrid in the parent window. When I want to refresh data from the iframe I call a function in the parent and the setRowData does not works. Some code:

function UpdateRow(id){

  var url = "dbserver.php?id="+id

  var datarow = $.ajax({url:url, async:false}).responseText;

  $("#DataGrid",parent.document).setRowData(id, datarow);

}

The datarow is:

{ID:'01',Name:'13.321321',Manufacturer:'2',Typ:'3',...}

In the grid nothing happens. Why, and what could be the solution?