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 ('c9371437ad84156229646abe50b5de8f', -1, 1397621432, 1397621432, '36c4d772', 7, 0)

Line : 170
File : sessions.php