SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Invalid SQL: INSERT INTO bb1_sessions (sessionhash,userid,ipaddress,useragent,lastactivity,request_uri,styleid,langid,authentificationcode, zone) VALUES ('3691b772970bf5830c3b0d76c0728c4c','0','38.107.191.95','CCBot/1.0 (+http://www.commoncrawl.org/bot.html)','1280599203','Mutterschaftsrichtlinien.htm','0','0','', 'F')
mysql error: Duplicate entry '3691b772970bf5830c3b0d76c0728c4c' for key 'PRIMARY'
mysql error number: 1062
mysql version: 5.1.47
php version: 5.3.2
Date: 31.07.2010 @ 20:00
Script: /Lexikon/Mutterschaftsrichtlinien.htm
Referer: