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 ('28574d7655ed6328a290d675c06cdf4f', -1, 1398390591, 1398390591, '36c4c448', 7, 0)

Line : 170
File : sessions.php