How can I hide the title in a custom page made with hook_menu?
Not sure if processed on time but I would try using drupal_set_title. And making sure you have an if statement around the h1 or h2. So use drupal_set_title to create empty title and use:

if(!empty($title)){
echo '&lt;h1&gt;' . $title . '&lt;/h1&gt;';
}