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 ('26ee23baf0fbc58a1a7fb7bb70aeeb26', -1, 1328362977, 1328362977, '266bb3ed', -2, 0, 0)

Line : 187
File : sessions.php