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) VALUES ('00613b4f01dedc16344500ecbae61854','0','38.107.191.94','CCBot/1.0 (+http://www.commoncrawl.org/bot.html)','1283992827','thread.php?postid=156161','0','1','')
mysql error: Duplicate entry '00613b4f01dedc16344500ecbae61854' for key 1
mysql error number: 1062
mysql version: 4.0.25-Max-log
php version: 4.4.9
Date: 09.09.2010 @ 02:40
Script: /wbb/thread.php?postid=156161
Referer: