I have a grid with 3 column groups and various columns assigned to each group.  At run time, the system generates the following exception when the user attempts to resize the column group: 

************** Exception Text **************
System.NullReferenceException: Object reference not set to an instance of an object.
   at Infragistics.Win.UltraWinGrid.HeaderUIElement.ApplyAdjustment(Point delta)
   at Infragistics.Win.AdjustableUIElement.OnMouseUp(MouseEventArgs e)
   at Infragistics.Win.UltraWinGrid.HeaderUIElement.OnMouseUp(MouseEventArgs e)
   at Infragistics.Win.ControlUIElementBase.ProcessMouseUpHelper(Object sender, MouseEventArgs e)
   at Infragistics.Win.ControlUIElementBase.ProcessMouseUp(Object sender, MouseEventArgs e)
   at Infragistics.Win.Utilities.ProcessEvent(Control control, ProcessEvent eventToProcess, EventArgs e)
   at Infragistics.Win.UltraControlBase.OnMouseUp(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

If the user attempts to resize a column within the group, it works fine.  Is there anyting I can do to stop this exception?