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 ('661e5daa9b1254a7d89445339f472cf8', -1, 1398074264, 1398074264, '3651aaba', 5, 0)

Line : 170
File : sessions.php