SQL-DATABASE ERROR

Database error in WoltLab Burning Board (2.3.6): Invalid SQL: INSERT INTO bb2_sessions (sessionhash,userid,ipaddress,useragent,lastactivity,request_uri,styleid,langid,authentificationcode) VALUES ('d1ace2386cfe9e3e7e9869ee60b7a997','0','38.103.63.60','CCBot/1.0 (+http://www.commoncrawl.org/bot.html)','1227362470','thread.php?threadid=34829','0','0','')
mysql error: Duplicate entry 'd1ace2386cfe9e3e7e9869ee60b7a997' for key 1
mysql error number: 1062
mysql version: 4.1.22-standard
php version: 4.4.9
Date: 22.11.2008 @ 15:01
Script: /thread.php?threadid=34829
Referer: