Duplicate child page

select * from {menu_links} where link_path = "node/150";
shows two entries, with 2 different mlid.

select * from {outline_node} where nid = 150;
shows one entry, with one of the above mlid.

Remove the extraneous one:
delete from {menu_links} where mlid = 366;

clear the cache (by editing a node).

fixed.