Error with postgresql 8.1

Always error on module that came with SELECT DISTINCT and ORDER BY

    * warning: pg_query() [function.pg-query]: Query failed: ERROR: for SELECT DISTINCT, ORDER BY expressions must appear in select list in /home/forum/drupal-6.9/includes/database.pgsql.inc on line 139.
    * user warning: query: SELECT DISTINCT u.uid, u.name, MAX(s.timestamp) FROM users u INNER 

JOIN sessions s ON u.uid = s.uid WHERE s.timestamp >= 1233798557 AND s.uid > 0 GROUP BY u.uid, u.name ORDER BY s.timestamp DESC in /home/forum/drupal-6.9/sites/all/modules/advanced_forum/advanced_forum.module on line 1612.
    * warning: pg_query() [function.pg-query]: Query failed: ERROR: operator does not exist: integer && integer HINT: No operator matches the given name and argument type(s). You may need to add explicit type casts. in /home/forum/drupal-6.9/includes/database.pgsql.inc on line 139.
    * user warning: query: SELECT uid, name FROM users WHERE status = 1 && access > 0 ORDER BY created DESC in /home/forum/drupal-6.9/sites/all/modules/advanced_forum/advanced_forum.module on line 1597.