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 ('a2988d254ff3e2171e966926e83b16a0', -1, 1328628495, 1328628495, '266bb3ed', 0, 0, 0)

Line : 187
File : sessions.php