phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO mex2mex_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in) VALUES ('15fc74bd10270baae4b39faa56ca25d9', -1, 1397655825, 1397655825, '36c445bd', 7, 0)

Line : 170
File : sessions.php