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 ('4276cb8b1b34c63907dede0fddc2881d', -1, 1406747518, 1406747518, '36cd77a3', 7, 0)

Line : 170
File : sessions.php