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 ('7fdd5838de92fec39766caca3ca2fc48', -1, 1406754769, 1406754769, '36cde112', 7, 0)

Line : 170
File : sessions.php