title: MessageBox.show() function doesn't work sometime
body: <p>My MessageBox.Show() function works well when I started to double click myApp.exe.
  But When I tried to attached the Application process with source code. and set breakpoint 
  At the code below, It doesn't work. What I mean is the MessageBox didn't pop-up. And the code catched by another outer exception handling. Does it caused by multi-threading timing issue?</p>
  
  <p>I don't know why?
  Thanks.</p>
  
  <pre><code>if (File.Exists(myConfigFile))
  {
      doc.Load(myConfigFile);
  }
  else
  {
      MessageBox.Show("Read " + myConfigFile + " failed, can't find the file",
      "Critical Warning",
      MessageBoxButtons.OK,
      MessageBoxIcon.Error);
  }
  </code></pre>