Database Error

[King Justice]

Please assist with this database error, is causing my forum not to function properly. New users can't register, people can't access PMs, and people can't view profiles...

Here it is:

PHP Code:

Database error in vBulletin 3.8.4:

Invalid SQL:

                SELECT user.*, (user.options & 512) AS invisible , avatar.avatarpath, NOT ISNULL(customavatar.userid) AS hascustom, customavatar.dateline AS avatardateline, customavatar.filedata_thumb, customavatar.height AS avheight, customavatar.width AS avwidth, customavatar.width_thumb AS avwidth_thumb, customavatar.height_thumb AS avheight_thumb
                    
                FROM userlist AS userlist
                INNER JOIN user AS user ON (user.userid = userlist.relationid)
                LEFT JOIN avatar AS avatar ON (avatar.avatarid = user.avatarid)
                LEFT JOIN customavatar AS customavatar ON (customavatar.userid = user.userid) 
                
                WHERE userlist.userid = 16236
                    AND userlist.type = 'buddy'
                    AND userlist.friend = 'yes'
                    
                ORDER BY RAND()
                LIMIT 0, 8;

MySQL Error   : Can't create/write to file '/tmp/#sql_10c6_0.MYI' (Errcode: 13)
Error Number  : 1
Request Date  : Sunday, January 10th 2010 @ 02:24:42 PM
Error Date    : Sunday, January 10th 2010 @ 02:24:42 PM
Script        : http://www.egamingsupply.com/forum/member.php?action=getinfo&u=16236
Referrer      : http://www.egamingsupply.com/forum/index.php
IP Address    : 68.39.148.100
Username      : Monarch
Classname     : vB_Database
MySQL Version : 5.0.51a-community