Watin DialogHandler closes SaveFileDialog

Based on this answer, I created a custom DialogHandlerJavascript to handle warning boxes that appear from a WebBrowser control.

Handlertied to a legacy WatiN browser IEcalled ExtendedIeBrowser.

For some unknown reason, watin DialogHandler intervenes in Winforms SaveFiledialogs. SaveFileDialogcloses automatically, returning DialogResult.Cancel. It is strange that a Handle()custom handler is never called. It CanHandle()is only called (twice) and returns false, so the dialog should not be processed at all, therefore it should remain open.

Is there anything I can do to change this weird behavior?

This is the source ExtendedIeBrowser:

public class ExtendedIeBrowser : IE
{
    private IntPtr hwnd;
    public ExtendedIeBrowser(WebBrowser webBrowserControl) : base(webBrowserControl.ActiveXInstance, false)
    {
    }

    public void Initialize(WebBrowser webBrowserControl)
    {
        hwnd = webBrowserControl.FindForm().Handle;
        StartDialogWatcher();
    }

    public override IntPtr hWnd { get { return hwnd; } }

    protected override void Dispose(bool disposing)
    {
        hwnd = IntPtr.Zero;
        base.Dispose(disposing);
    }
}

After the source CustomPopupDialogHandler:

class CustomPopupDialogHandler : ReturnDialogHandler
{
    protected static Logger _logger = LogManager.GetCurrentClassLogger();

    public override bool HandleDialog(Window window)
    {
        bool handled = false;
        try
        {
            var button = GetWantedButton(window);
        if (button != null)
        {
            button.Click();
        }
            handled = true;
        }
        catch (Exception ex)
        {
            _logger.ErrorException("HandleDialog", ex);
        }
        return handled;
    }

    public override bool CanHandleDialog(Window window)
    {
        bool canHandle = false;
        try
        {
        canHandle = GetWantedButton(window) != null;
        }
        catch (Exception ex)
        {
            _logger.ErrorException("CanHandleDialog", ex);
        }
        return canHandle;
    }

    private WinButton GetWantedButton(Window window)
    {
        WinButton button = null;
        try
        {
            if (window.Title.Contains("Windows Internet Explorer") || window.Title.Contains("Message from webpage"))
            {
                var windowButton = new WindowsEnumerator().GetChildWindows(window.Hwnd, w => w.ClassName == "Button" && (new WinButton(w.Hwnd).Title.Contains("Leave") || new WinButton(w.Hwnd).Title.Contains("OK")).FirstOrDefault();
                if (windowButton != null)
                {
                    string s = windowButton.Title;
                    button = new WinButton(windowButton.Hwnd);
                }
            }
        }
        catch (Exception ex)
        {
            _logger.ErrorException("GetWantedButton", ex);
        }
        return button;
    }
}