An odd error in MySQL.. (thread.MYI?)

[Velocd]

It seems some strange outside interference has caused my forum to temporarily shut down.

I am receiving a strange database error that says:

Database error in vBulletin 2.3.0:

Invalid SQL: 
  SELECT threadid,forumid,title,replycount,postusername,dateline,views,postuserid
  FROM thread
  WHERE visible=1 AND open<>10 
  ORDER BY dateline DESC LIMIT 8

mysql error: Can't open file: 'thread.MYI'. (errno: 145)

mysql error number: 1016

Date: Monday 07th of April 2003 09:22:23 PM
Script: http://www.animesystem.com/forums/
Referer:

I'm not sure what it is referring to when it says "thread.MYI"

Anyone have any ideas? The most recent thing I've done was create a new subdomain on my server, but I hardly see how this could be causing a problem. I was browsing a thread on my site at school today and it loaded just fine, but sometime between 7 hours ago and now this error occurred.

Thanks if you can help.