We have an MDI application that uses an UltraTree object to display hierarchical functions to user. About a month ago, we upgraded our Infragistics components to the latest release, 11.2 CLR 4.0, SR 2028. 

We're now experiencing a random error, that appears during mouse operations (mouse move, mouse click) on UltraTree, and that is intercepted by OS as an Unhandled exception:

System.ObjectDisposedException: Cannot access a disposed object.
Object name: 'ToolTipFormEx'.
   at System.Windows.Forms.Control.CreateHandle()
   at System.Windows.Forms.Form.CreateHandle()
   at Infragistics.Win.ToolTipForm.CreateHandle()
   at System.Windows.Forms.Control.RecreateHandleCore()
   at System.Windows.Forms.Form.RecreateHandleCore()
   at Infragistics.Win.ToolTipFormEx.set_DisplayShadow(Boolean value)
   at Infragistics.Win.ToolTip.set_DisplayShadow(Boolean value)
   at Infragistics.Win.UltraWinTree.UltraTree.get_ToolTip()
   at Infragistics.Win.UltraWinTree.UltraTreeNode.ShowTooltipIfNeeded()
   at Infragistics.Win.UltraWinTree.UltraTree.OnMouseEnterElement(UIElementEventArgs e)
   at Infragistics.Win.UltraControlBase.Infragistics.Win.IUltraControl.FireMouseEnterElement(UIElementEventArgs e)
   at Infragistics.Win.ControlUIElementBase.ElementEntered(UIElement element, Boolean triggerMouseLeavesOnly)
   at Infragistics.Win.ControlUIElementBase.ProcessMouseMoveHelper(Object sender, mouseEventArgs e)
   at Infragistics.Win.ControlUIElementBase.ProcessMouseMove(Object sender, MouseEventArgs e)
   at Infragistics.Win.Utilities.ProcessEvent(Control control, ProcessEvent eventToProcess, EventArgs e)
   at Infragistics.Win.UltraWinTree.UltraTree.OnMouseMove(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseMove(Message& m)
   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)

Could you please help us to avoid this behaviour? If you need details, please ask.
Thanks!