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 ('16a0ed8432036ee0fc4b5d3d1cc70c4c', -1, 1280443197, 1280443197, '266bbf54', 7, 0, 0)

Line : 187
File : sessions.php