Turning on multiple search weights causes PDO exception during search

If I set more than one weight to > 0 on the search configuration page, the node search fails and the dblog has an error message like:

PDOException: SQLSTATE[HY093]: Invalid parameter number: number of bound variables does not match number of tokens: SELECT i.type AS type, i.sid AS sid, SUM(CAST(:multiply_0 AS DECIMAL) * COALESCE(( 2.0 - 2.0 / (1.0 + node_comment_statistics.comment_count * CAST(:scale AS DECIMAL))), 0) / CAST(:total_0 AS DECIMAL) + CAST(:multiply_1 AS DECIMAL) * COALESCE(( POW(2.0, (GREATEST(n.created, n.changed) - :node_cron_last) * 6.43e-8)), 0) / CAST(:total_1 AS DECIMAL)) AS calculated_score FROM {search_index} i INNER JOIN {node} n ON n.nid = i.sid INNER JOIN {search_total} t ON i.word = t.word LEFT JOIN {node_comment_statistics} node_comment_statistics ON node_comment_statistics.nid = i.sid INNER JOIN {search_dataset} d ON i.sid = d.sid AND i.type = d.type WHERE (n.status = :db_condition_placeholder_0) AND( (i.word = :db_condition_placeholder_1) )AND (i.type = :db_condition_placeholder_2) AND( (d.data LIKE :db_condition_placeholder_3 ESCAPE '\\') ) GROUP BY i.type, i.sid HAVING (COUNT(*) >= :matches) ORDER BY calculated_score DESC LIMIT 10 OFFSET 0; Array ( [:db_condition_placeholder_0] => 1 [:db_condition_placeholder_1] => blog [:db_condition_placeholder_2] => node [:db_condition_placeholder_3] => % blog % [:matches] => 1 [:scale] => 0 [:multiply_0] => 4 [:node_cron_last] => 1271277590 [:multiply_1] => 6 [total_0] => 10 )  in PagerDefault->execute() (line 93 of /mnt/www/html/tangle001/docroot/includes/pager.inc).