What is this database error saying?

[YankForum]

hello
for last few days i'm having hundreds of this error reporting to my email but i have not changed anything , i dont know what caused this , please have a look and let me know if u have any clue :

Database error in vBulletin 4.0.6:

Invalid SQL:

                               SELECT thread.threadid, thread.title, thread.prefixid, post.attach,
                                       thread.postusername, thread.dateline, thread.lastpostid, thread.lastpost, thread.lastposterid, thread.lastposter, thread.replycount,
                                       forum.forumid, forum.title_clean as forumtitle,
                                       post.pagetext AS message, post.allowsmilie, post.postid,
                                       user.*
                                       ,avatar.avatarpath, NOT ISNULL(customavatar.userid) AS hascustomavatar, customavatar.dateline AS avatardateline,customavatar.width AS avwidth,customavatar.height AS avheight
                               FROM thread AS thread
                               INNER JOIN forum AS forum ON(forum.forumid = thread.forumid)
                               LEFT JOIN post AS post ON (post.postid = thread.firstpostid)
                               LEFT JOIN user AS user ON (thread.postuserid = user.userid)
                               LEFT JOIN avatar AS avatar ON(avatar.avatarid = user.avatarid) LEFT JOIN customavatar AS customavatar ON(customavatar.userid = user.userid)
                       WHERE 1=1
                               AND thread.forumid IN(46,47,48,74,72,71,76,77,94,75,90,89,91,92,97,99,88,93,87,96,95,64,59,40,43,73,81,80,82,83,63,57,58,56,70,42,69,50,49,51,53,54,52,55,44,78,79,41,45,84,85,86,3,6,4,5,98,7)
                               AND thread.visible = 1
                               AND post.visible = 1
                               AND open <> 10
                                AND thread.lastpost > 1299662410


                       ORDER BY thread.lastpost DESC
                       LIMIT 0,5;

MySQL Error   : Incorrect key file for table '/tmp/#sql_502d_1.MYI'; try to repair it
Error Number  : 126
Request Date  : Friday, April 8th 2011 @ 02:20:10 AM
Error Date    : Friday, April 8th 2011 @ 02:20:10 AM
Script        : http://www.******.com/
Referrer      :
IP Address    : ******
Username      : Unregistered
Classname     : vB_Database
MySQL Version :