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) VALUES ('29fb9f97bcf23d009b1a33075dbce92d', -1, 1409675991, 1409675991, 'ccecfe7c', 35, 0)

Line : 315
File : sessions.php