I have a simple WinForms app that is used to enter test cases. Ever since I upgraded this application to .NET 4.0 and added a new tab page to the tab page control for validating XML against XSD schema the application has been randomly crashing. I've been unable to reproduce the exception.

The error my QA guy receives is the generic Windows message:

TestCaseViewer has encountered a problem and needs to close. We are sorry for the inconvenience.

To try to get to the real error I've added the following code to the beginning of the Main method of program:

```
        AppDomain.CurrentDomain.UnhandledException += CurrentDomain_UnhandledException;
        Application.SetUnhandledExceptionMode(UnhandledExceptionMode.CatchException);
        Application.ThreadException += Application_ThreadException;

```

The event handlers look like this:

```
    static void Application_ThreadException(object sender, ThreadExceptionEventArgs e)
    {
        try
        {
            MessageBox.Show(e.Exception.ToString(), @"Thread Exception", 
                MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
        }
        finally 
        {
            Application.Exit();    
        }
    }

    static void CurrentDomain_UnhandledException(object sender, UnhandledExceptionEventArgs e)
    {
        try
        {
            var ex = (Exception)e.ExceptionObject;
            MessageBox.Show(ex.ToString(), @"Unhandled Exception",
                MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
        }
        finally 
        {
            Application.Exit();    
        }
    }

```

Unfortunately this hasn't helped and whatever is thowing the error continues to do so in a way that generates the unhandled error that is bubbling up to the OS.

Can anyone give me any other ideas about trapping this exception?