I have a FreeForm tree for which I manually generate the Column sets and everything. Within tree_AfterExpand() handler I execute the following (to size all of the columns of the expanded node):

 if (e.TreeNode.HasNodes)
  {

           foreach (UltraTreeNodeCell cell in e.TreeNode.Nodes[0].Cells)
            {

                cell.Column.PerformAutoResize(

                Infragistics.Win.UltraWinTree.ColumnAutoSizeMode.VisibleNodes);

            }                   
     }

which results in the following exception. Any ideas? Thanks.