vBulletin Database Error!‏

[KimK]

Hello,

Im getting alot of vBulletin Database Error‏ emails, about 60 email daily with the following error:

Database error in vBulletin 4.2.2:


Invalid SQL:
 
			SELECT user.*, discussion.discussionid, discussion.groupid, discussion.lastpostid, discussion.lastpost,
				discussion.lastposter, discussion.lastposterid, discussion.visible,
				groupmessage.gmid, groupmessage.postuserid, groupmessage.postusername, groupmessage.dateline,
				groupmessage.title, groupmessage.pagetext as message,
				socialgroup.name as groupname, socialgroup.description as groupdescription
				,avatar.avatarpath, NOT ISNULL(customavatar.userid) AS hascustomavatar,
					customavatar.dateline AS avatardateline,customavatar.width AS avwidth,customavatar.height AS avheight
			FROM discussion AS discussion
			INNER JOIN socialgroup AS socialgroup ON(discussion.groupid = socialgroup.groupid)
			INNER JOIN groupmessage AS groupmessage ON (discussion.firstpostid = groupmessage.gmid)
			LEFT JOIN user AS user ON (groupmessage.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 ( !(socialgroup.options & 1))
			AND discussion.visible > 0
			AND groupmessage.state = 'visible'
			 AND groupmessage.dateline > 130000858
			
		ORDER BY groupmessage.dateline DESC
		LIMIT 0,5;
 
MySQL Error   : Got error 28 from storage engine
Error Number  : 1030
Referrer      : 
Classname     : vB_Database
MySQL Version :

What should I do to fix this error?? I contact my hosting company and they replied with: "The error in question indeed appears when there is not enough free space in the /tmp partition of the server. We have increased the size of the /tmp/ folder and the issue should not reappear.".

But Im still getting the vBulletin Database Error‏ emails. Can any one help me please.