I hope you find this useful, It worked with me. Beside I didn't like this mess about .Control[0].Control[1]...

this is much easier and it working perfectly.

protected void Login1_Authenticate(object sender, AuthenticateEventArgs e)
    {
        Login Login1 = ((Login)LoginView1.FindControl("Login1"));
        string userName = Login1.UserName.ToString();
        string password = Login1.Password.ToString();
      

        if (Membership.ValidateUser(userName, password))
        {
            if (Request.QueryString["ReturnUrl"] != null)
            {
                FormsAuthentication.RedirectFromLoginPage(userName, true);
            }
            else
            {
                FormsAuthentication.SetAuthCookie(userName, true);
                Response.Redirect("~/Default.aspx");
            }
        }
        else
        {
            Label lblResults = (Label)Login1.FindControl("lblResults");
            lblResults.Visible = true;
            lblResults.Text = "regarding that you have only 5 times to try";
            if ((Membership.GetUser(userName) != null) && (Membership.GetUser(userName).IsLockedOut == true))
                lblResults.Text = "  <b>Your account has been locked out.</b>";
        }
    }

 ;)

Dont forget to mark it as answer if it helps !