Database error in vBulletin 3.8.6

[downloadsguru]

Hello can any one please guide me in fixing this error

Invalid SQL:

     SELECT thread.threadid,
            thread.title AS tht,
            thread.postusername,
            thread.replycount,
            thread.lastposter,
            thread.views,
            thread.attach,
            forum.title AS fot
     FROM thread AS thread, forum AS forum
     WHERE thread.forumid = forum.forumid
     AND thread.forumid NOT IN (45,62,73,5,86,91,92,93,94,95,76,79,81,97,107,108,16,109)
     AND thread.threadid NOT IN (0)
     order by thread.dateline Desc
     LIMIT 100;

MySQL Error   : Error writing file '/tmp/MY5HXdB5' (Errcode: 28)
Error Number  : 3
Request Date  : Monday, August 22nd 2011 @ 04:19:10 PM
Error Date    : Monday, August 22nd 2011 @ 04:19:12 PM
Script        : http://www.downloadsguru.com/index.php
Classname     : vB_Database
MySQL Version : 5.0.92-community

Thanx in advance