Database error in PM's

[newmasalaboard]

Hello,

Actually whenever we open inbox or something related to private messaging the we are facing a DB error.Its says :

Database error in vBulletin 3.7.0:

Invalid SQL:

            SELECT pm.*, pmtext.*
                , icon.title AS icontitle, icon.iconpath
            FROM pm AS pm
            LEFT JOIN pmtext AS pmtext ON(pmtext.pmtextid = pm.pmtextid)
            LEFT JOIN icon AS icon ON(icon.iconid = pmtext.iconid)
            WHERE pm.userid=1 AND pm.folderid=0
            ORDER BY pmtext.dateline DESC
            LIMIT 0, 50;

MySQL Error   : Can't create/write to file '/tmp/#sql_c72_0.MYI' (Errcode: 30)
Error Number  : 1
Request Date  : Tuesday, August 12th 2008 @ 05:20:22 AM
Error Date    : Tuesday, August 12th 2008 @ 05:20:22 AM
Script        : http://www.newmasalaboard.info/private.php
Referrer      : http://www.newmasalaboard.info/private.php
IP Address    : XXXXXXXXX
Username      : XXXXXXXXX
Classname     : vB_Database
MySQL Version : 5.0.51a-community

Please help me to solve the problem !!