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 ('c750978f95e6f64402d8315d6b7d0729', -1, 1369335949, 1369335949, '36ea7e5c', 2, 0, 0)

Line : 187
File : sessions.php