One of our testers is getting an unhandled exception deep in the Infragistics UltraExploereBar class while trying to expand the UltraExplorerBar.  Our code is never even executed.

I can not reproduce the error.  The user opens our applications.  Then they let the application set idel for 45 min to an hour.  Next the user collapses the explorer bar.  Finally when the user expands the exploer bar and they get the error below.

This hapens about half the time.  Any help woudl be greatly appriciated.

Stack (unfortunately the image the user sent me was cut off)

System.ArgumentException: ActiveGroup cannot be set - specified Group caoonot be
  at Infragistics.Win.UltraWinExplorerBar.UltraExplorerBar.set_ActiveGroup(UltraExplo
  at Infragistics.Win.UltraWinExplorerBar.UltraExplorerBarGroupHeaderUIElement.O
  at Infragistics.Win.ControlUIElementBase.ProcessMouseDownHelper(Object send
  at Infragistics.Win.ControlUIElementBase.ProcessMouseDown(Object sender, Mou
  at Infragistics.Win.Utilities.ProcessEvent(Control control, ProcessEvent eventToPro
  at Infragistics.Win.UltraControlBase.OnMouseDown(MouseEventArgs e)
  at Infragistics.Win.UltraWinExplorerBar.UltraExplorerBar.OnMouseDown(MouseEv
  at System.Windows.Forms.Control.WmMouseDown(Message& m, MouseButtons b
  at System.Windows.Forms.Control.WndProc(Message& m)
  at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m
  at System.Windows.Forms... (and so on...)