Hello i got de next exception with a simple code like this, a DataTable binded to a UltraGrid and then insert and remove rows from the DataTable, the exception doesn't always occur or it takes different time to happen after the program is running. 

      this.ultraGrid1.DataSource = this._historico;
      this.ultraGrid1.DataBind();

...............

  if (this._historico.Rows.Count == 10)
     {
        this._historico.Rows.InsertAt(dr, 0);
        this._historico.Rows.RemoveAt(this._historico.Rows.Count - 1);
     }
     else
     {
        this._historico.Rows.InsertAt(dr, 0);

     }

System.NullReferenceException: Object reference not set to an instance of an object.
   en Infragistics.Win.UltraWinGrid.UltraGrid.Infragistics.Win.ISelectionManager.GetPivotItem(ISelectableItem item)
   en Infragistics.Win.UltraWinGrid.UltraGrid.Infragistics.Win.ISelectionManager.SetPivotItem(ISelectableItem item, Boolean IsRangeSelect)
   en Infragistics.Win.UltraWinGrid.UltraGrid.OnActiveRowChange(UltraGridRow newActiveRow, Boolean scrollIntoView)
   en Infragistics.Win.UltraWinGrid.UltraGridBase.SetActiveRow(UltraGridRow row, Boolean scrollIntoView)
   en Infragistics.Win.UltraWinGrid.UltraGrid.EnsureTempActiveRowAssigned()
   en Infragistics.Win.UltraWinGrid.UltraGrid.OnPaint(PaintEventArgs pe)
   en System.Windows.Forms.Control.PaintWithErrorHandling(PaintEventArgs e, Int16 layer, Boolean disposeEventArgs)
   en System.Windows.Forms.Control.WmPaint(Message& m)
   en System.Windows.Forms.Control.WndProc(Message& m)
   en System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   en System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   en System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

i hope, someone could give a clue. Thanks