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 ('5d28fb6dd1f03f9006efb768fc84e4aa', -1, 1398318443, 1398318443, '171414c3', 7, 0)

Line : 170
File : sessions.php