Cron problems

Hi I was looking at the issues, but didn't find answer to my problem. Every time I run the cron I receive the following message

* user warning: Table 'meta_data' already exists query: CREATE TEMPORARY TABLE meta_data Engine=HEAP SELECT GREATEST(IF(c.last_comment_timestamp IS NULL, 0, c.last_comment_timestamp), n.changed) as last_change, n.nid, n.created, SQRT(SUM(POW(s.score,2))) as mag FROM node n LEFT JOIN node_comment_statistics c ON n.nid = c.nid INNER JOIN search_index s ON s.type = 'node' AND s.sid = n.nid WHERE n.status = 1 AND ((GREATEST(n.changed, c.last_comment_timestamp) = 1257289921) OR (n.changed > 1257289921 OR c.last_comment_timestamp > 1257289921)) AND (n.type = 'forum') GROUP BY n.nid ORDER BY GREATEST(n.changed, c.last_comment_timestamp) ASC, n.nid ASC LIMIT 0, 100 in /home/cartrite/public_html/fleetsurveys/finalsurvey/sites/all/modules/similarity/classes/similarity_search_similarity.inc on line 47.
* user warning: Multiple primary key defined query: ALTER TABLE meta_data ADD PRIMARY KEY(nid) in /home/cartrite/public_html/fleetsurveys/finalsurvey/sites/all/modules/similarity/classes/similarity_search_similarity.inc on line 48.
* user warning: Table 'local_mag' already exists query: CREATE TEMPORARY TABLE local_mag Engine=HEAP SELECT sid as nid, SQRT(SUM(POW(score,2))) as mag FROM search_index WHERE type = 'node' GROUP BY sid in /home/cartrite/public_html/fleetsurveys/finalsurvey/sites/all/modules/similarity/classes/similarity_search_similarity.inc on line 51.
* user warning: Multiple primary key defined query: ALTER TABLE local_mag ADD PRIMARY KEY(nid) in /home/cartrite/public_html/fleetsurveys/finalsurvey/sites/all/modules/similarity/classes/similarity_search_similarity.inc on line 54.