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 ('4896787fd2ab9d1d44a8278ac418483b', -1, 1406659699, 1406659699, '3653e718', 1, 0, 0)

Line : 172
File : sessions.php