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 ('bbb70c4a7139f8c872cc2c0d06f2bae7', -1, 1257616378, 1257616378, '266bbf58', 7, 0, 0)

Line : 234
File : sessions.php