Edit the .xml file on your hard drive. Change this code:
HTML Code:
<installcode><![CDATA[$vbulletin->db->query("ALTER TABLE `" . TABLE_PREFIX . "usergroup` ADD `unreq_perms` INT( 10 ) UNSIGNED DEFAULT '0' NOT NULL") ;]]></installcode>
to:
HTML Code:
<installcode><![CDATA[//$vbulletin->db->query("ALTER TABLE `" . TABLE_PREFIX . "usergroup` ADD `unreq_perms` INT( 10 ) UNSIGNED DEFAULT '0' NOT NULL") ;]]></installcode>
That should fix your problem if you are getting that error.