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 ('de5cd0f19cb089dcc5044b6ede8f7856', -1, 1284023713, 1284023713, '266bbf75', 0, 0, 0)

Line : 187
File : sessions.php