phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('cad9a6080098154068fd789dd2ede6a7', -1, 1406835296, 1406835296, '36f27047', 5, 0, 0)

Line : 187
File : sessions.php