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 ('dadd01cddfc8f38ba42c703e9458c85f', -1, 1406849943, 1406849943, '36e10146', 35, 0)

Line : 315
File : sessions.php