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 ('4e6f9cfb2822da82d0484355c7b2678d', -1, 1398329568, 1398329568, '365385bd', 7, 0)

Line : 170
File : sessions.php