Database error
 

I'm getting this database error when trying to get to my site:
Quote:
Database error in vBulletin 3.8.2:

Invalid SQL:

SELECT COUNT(post.dateline) AS postcount, post.userid, user.userid,
user.username, user.lastpost, user.lastpostid, user.posts, user.usergroupid,
IF(displaygroupid=0, usergroupid, displaygroupid) AS displaygroupid
FROM vb_post AS post
LEFT JOIN vb_user AS user ON (post.userid = user.userid)


WHERE dateline > 1242622800 AND user.posts != '0'
GROUP BY post.userid
ORDER BY postcount DESC
LIMIT 0, 10;

MySQL Error : Out of memory (Needed 6348020 bytes)
Error Number : 5
Request Date : Monday, May 18th 2009 @ 04:06:56 AM
Error Date : Monday, May 18th 2009 @ 04:06:59 AM
Script : http://www.braves-nation.com/forums/
Referrer :
IP Address : ******
Username : ******
Classname : vB_Database
MySQL Version : 5.0.41-community-log
I went into the ACP and optimized/repaired the tables and it corrected itself for a moment, but then came back. What would be the more permanent solution?