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 ('c64e4d18e98f5f423216210a71e5428d', -1, 1398355708, 1398355708, '36ed863e', 9, 0)

Line : 170
File : sessions.php