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 ('f8a8acc457bbf7f2b061bfcb78762e4c', -1, 1409718948, 1409718948, '36e285c4', -1, 0, 0)

Line : 172
File : sessions.php