title: MessageBox.Show issue
body: <p>I have a lot of code like this and it usually works</p>
  
  <pre><code>private void button_Click(object sender, EventArgs e)
  {
      try
      {
          DialogResult result;
          result = MessageBox.Show( "Questa operazione potrebbe richiedere alcuni minuti,\r\nsei sicuro di voler continuare?", "Attenzione", MessageBoxButtons.YesNo, MessageBoxIcon.Warning );
          if ( result == System.Windows.Forms.DialogResult.Yes )
          {
              DoSomething();
          }
          else
          {
              DoSomethingElse();
          }
      }
      Catch (Exception ex)
      {
          LogExceptio(ex);
      }
  } 
  </code></pre>
  
  <p>but for some reason on a specific <code>Windows Form</code> the <code>MessageBox</code> is not showing.
  If I press <kbd>Enter</kbd> it proceed like I have made a click on YES;
  If I press the <kbd>ALT</kbd> key the MessageBox magically appear on the screen.</p>
  
  <p>Any idea?
  What can I do to solve this issue?</p>