I am also having some problem:
add_action('activate_'.$this->tmh_pi_path, array(&$this, 'tmhpiActivate'));
add_action('edit_form_advanced', array(&$this, 'tmhpiCustomFields'));
add_action('edit_page_form', array(&$this, 'tmhpiCustomFields'));
add_action('edit_post', array(&$this, 'tmhpiMetaboxHandle'));
It was working perfecting fine before with 2.9 but when I upgrade it to 3.0 then suddenly it does not show a form field in below the post form in admin.