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 ('7aff966ba54139f8896fdc6e5ca1354f', -1, 1257634636, 1257634636, '266bbf57', 17, 0, 0)

Line : 234
File : sessions.php