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 ('a0d6dc70bc091d839d3072e344f5fec4', -1, 1398410456, 1398410456, '36cc4226', 7, 0)

Line : 170
File : sessions.php