sql error when setting and use wikitools modul

Gnu/debian Lenny, apache2, suphp, postgresql

* warning: pg_query() [function.pg-query]: Query failed: ERREUR: la colonne « _ » n'existe pas LINE 1: ...de n1, node n2 WHERE LOWER(REPLACE(n1.title, "_", " "))... ^ in ...../includes/database.pgsql.inc on line 139.
* user warning: query: SELECT COUNT(DISTINCT(n1.nid)) FROM node n1, node n2 WHERE LOWER(REPLACE(n1.title, "_", " ")) = LOWER(REPLACE(n2.title, "_", " ")) AND n1.nid != n2.nid AND n1.type IN('wiki') AND n2.type IN('wiki') in /...../modules/wikitools/wikitools.admin.inc on line 17.