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 ('897fe6e7793edb424fe29890158f7ad9', -1, 1398074265, 1398074265, '3651aaba', 5, 0)

Line : 170
File : sessions.php