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 ('3a1f57d52e36a6dc6e4b0f0828e0c3e1', -1, 1268313611, 1268313611, '266bbf5b', -1, 0, 0)

Line : 187
File : sessions.php