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 ('1f9d0f09964f53d7c01f2c65f6c927ef', -1, 1257627438, 1257627438, '266bbf57', 7, 0, 0)

Line : 234
File : sessions.php