I have explorer bar on left, form on right.  If form is dirty and user clicks on left navigation pan, I need to validate if form is dirty and display message to either continue displaying the form or disposing it. Here is what happens

1. item1 in navigation pane on left is selected that displayes Form on right.
2. Form data is edited so it turns dirty
3. User clicks on item2 in navigation pane on left.
4. At this point item_clicked event does not get raised but rather Forms's On Validating is raised.
5. I display messagebox to continue or exit form editing.I chose exit form editing
6. At this point Explorer bar is in this weird state where item2 is selected but its' selected event never gets called where I hope to change background of item2 and reset background of item1
7. That when if User clicks anywhere following appears!!! 

System.NullReferenceException: Object reference not set to an instance of an object.
   at Infragistics.Win.UltraWinExplorerBar.c(Point point)
   at Infragistics.Win.UltraWinExplorerBar.UltraExplorerBar.Infragistics.Win.UltraWinExplorerBar.IItemContainer.ItemFromPoint(Point point)
   at Infragistics.Win.UltraWinExplorerBar.UltraExplorerBar.OnMouseDownHelper(IItemContainer itemContainer, MouseEventArgs e)
   at Infragistics.Win.UltraWinExplorerBar.UltraExplorerBar.OnMouseDown(MouseEventArgs e)
   at System.Windows.Forms.Control.WmMouseDown(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.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at Infragistics.Practices.CompositeUI.WinForms.IGFormShellApplication`2.Start()
   at Microsoft.Practices.CompositeUI.CabApplication`1.Run()
   at Aramark.Applications.HealthConnect.WinUI.Infrastructure.Shell.ShellApplication.RunInDebugMode() in