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 ('c51c2259ac5eb01ebcf1470daf166c18', -1, 1406050805, 1406050805, '36e33fc3', 7, 0)

Line : 170
File : sessions.php