Anyone see this before.

phpBB : Critical Error

Error creating new session

DEBUG MODE

SQL Error : 1016 Can't open file: 'phpbb_sessions.MYI'. (errno: 145)

INSERT INTO phpbb_sessions (session_id, session_user_id, session_start, session_time, session_ip, session_page, session_logged_in, session_admin) VALUES ('3bf7af01fc9b400ec21bbf75b38ab472', -1, 1189907200, 1189907200, '445a7905', 0, 0, 0)

Line : 188
File : sessions.php

How does one recover from this? Is there a program that will restore normal ops? Is this just a corruption or a hacking??

This is on a friends site and I know next to nothing about this.