MyBB SQL Error

MyBB has experienced an internal SQL error and cannot continue.

SQL Error:
1062 - Duplicate entry '0' for key 2
Query:
REPLACE INTO bb_sessions SET `uid`='0',`sid`='4bae12c2f44656b3476b42cf6a90f0d0',`time`='1414767575',`ip`='54.82.121.218',`location`='/forums/index.php?',`useragent`='CCBot/2.0 (http://commoncrawl.org/faq/)',`location1`='0',`location2`='0',`nopermission`='0'