Pm problems

[almac]

Got error message when tried to send pm

Database error in vBulletin 3.6.5:

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=7910 AND pm.folderid=0
ORDER BY pmtext.dateline DESC
LIMIT 0, 50;

MySQL Error : Can't create/write to file '/tmp/#sql_67a9_0.MYD' (Errcode: 17)
Error Number : 1

What do i do?