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 ('55ad705dc2dd6e7c6a3acbcabf5a408e', -1, 1406886484, 1406886484, '36cc7f38', 27, 0)

Line : 170
File : sessions.php