Hi,
I have not done anything with the configuration panel nor have I tested the rest of the plugin extensively with the changes. That might perhaps be a good idea to do 
the changes I made were in includes/module.php line 447:
add_submenu_page('newsletter_main_index', $title, $title, 'manage_options', $name, $name);
and line 459
add_submenu_page(null, $title, $title, 'manage_options', $name, $name);
and in plugin.php on line 218
add_menu_page('Newsletter', 'Newsletter', 'manage_options', 'newsletter_main_index');
Hope this helps and comes right through testing 
Sincerely, Simone
