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 ('7480e8d3c67c8438f0151b2327d31425', -1, 1397633522, 1397633522, '36c445bd', 7, 0)

Line : 170
File : sessions.php