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 ('3981cbac9003b61c21838d472db8c4d2', -1, 1406667082, 1406667082, '365a7f0a', 7, 0)

Line : 170
File : sessions.php