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 ('1870ff454a57f34f11f66f9034b3acd0', -1, 1409556417, 1409556417, '1714d399', -1, 0, 0)

Line : 172
File : sessions.php