Since the error seems to suggest that mysql_free_result is used directly in the hook, rather than $db->free_result, I would imagine the issue is related to one of the PhotoPost or ReviewPost mods. As these are both paid modifications without Lite versions, I cannot test them to see why. So I don't know if the issue will be limited to the installer or not. But if you could provide access to your test board, I might be able to work out a solution on the VaultWiki end, or at least point you or the developers of the other mod in the right direction. If that's possible, please fill out a Support Ticket service via the Members tab.