phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1062 Duplicate entry '-1' for key 2

INSERT INTO mex2mex_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in) VALUES ('178c23b17c5cf9db99b932e1ffa2846c', -1, 1406740185, 1406740185, '6b15bb83', 7, 0)

Line : 170
File : sessions.php