Forum OpenACS Development: integrity violation

I get the following error ERROR: cr_type_children_parent_fk referential integrity violation - key in acs_object_types still referenced from cr_type_children from this code

create function inline_10 ()
returns integer as'
begin
  PERFORM acs_object_type__drop_type(''cr_wp_presentation'',''f'');
  PERFORM
acs_object_type__drop_type(''cr_wp_presentation_audience'',''f'');
  PERFORM
acs_object_type__drop_type(''cr_wp_presentation_background'',''f'');
  PERFORM acs_object_type__drop_type(''cr_wp_slide'',''f'');
  PERFORM acs_object_type__drop_type(''cr_wp_slide_preamble'',''f'');
  PERFORM acs_object_type__drop_type(''cr_wp_slide_postamble'',''f'');
  PERFORM
acs_object_type__drop_type(''cr_wp_slide_bullet_items'',''f'');
return 0;
end;' language 'plpgsql';
select inline_10 ();
drop function inline_10 ();