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 ('4961f6ea0a8d2359c3cf945e2b872b42', -1, 1406747525, 1406747525, '36cd77a3', 0, 0)

Line : 170
File : sessions.php