phpBB : Critical Error

Error creating new session

DEBUG MODE

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

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('26c9ad14df6804a79db1a961a35537a1', -1, 1722048848, 1722048848, '1276cfb7', -4, 0, 0)

Line : 172
File : /home/rebkell/public_html/boards/includes/sessions.php