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 ('f78b355ddb9e4851eb071e53cba4e06e', -1, 1406242689, 1406242689, '3650eb49', 7, 0)

Line : 170
File : sessions.php