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 ('9f88e2f9fdd55dca7a66a3c8c39f44a8', -1, 1406740181, 1406740181, '6b15bb83', 7, 0)

Line : 170
File : sessions.php