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 ('4b3d991dcf7204a6fb16b6f98c2108a1', -1, 1265704981, 1265704981, '266bbf76', 0, 0, 0)

Line : 187
File : sessions.php