trouble backing up database via adminCP

[Rickie3]

hi i'm getting this error trying to back-up my database via admin CP

Database error in vBulletin 3.5.0:

Invalid SQL:
SELECT * FROM sg_attachment;

MySQL Error : MySQL client run out of memory
Error Number : 2008
Date : Monday, November 14th 2005 @ 07:15:45 AM
Script : http://***************/forum/admincp/backup.php

Database error in vBulletin 3.5.0:

Invalid SQL:

UPDATE sg_session
SET lastactivity = 1131970541, inforum = 0, inthread = 0, incalendar = 0, badlocation = 0
WHERE sessionhash = '190a441624e4005ca1495a6ecefca171';

MySQL Error : Lost connection to MySQL server during query
Error Number : 2013
Date : Monday, November 14th 2005 @ 07:15:45 AM
Script : http://*****************/forum/admincp/backup.php


anyone got any ideas as to what could be causing this