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 ('f2d3e3cc926fb2566db197a557cf4b81', -1, 1398240826, 1398240826, '36cc86b7', 7, 0)

Line : 170
File : sessions.php