Incorrect key file for table mysql errors

[NeverBored]

Suddenly I'm getting a bunch of these errors every day for the past week. It's not constant, but seemingly random I'll get 1+ error emails at a time. From the looks of it I'm not sure that it's a VB problem directly, but I'm really just hoping someone can help me out. I don't understand where the table it quotes is or how to repair it... The query listed is a plugin that grabs a list of 5 threads, is there something wrong with it? It works, and I've been using it for like a year.

Invalid SQL:
SELECT * FROM thread WHERE ytvideo AND forumid IN (13) AND open=1 ORDER BY RAND() DESC LIMIT 5;

Incorrect key file for table '/var/mysqltmp/#sql_45a7_6.MYI'; try to repair it