Conflicts with wp-admin/includes/upgrade.php

If I activate the “Custom Post Type Maker” plugin and also activate a plugin with:
require_once(ABSPATH . 'wp-admin/includes/upgrade.php');

In the activation, and then I try to add another plugin using “add new” plugin I get the marvelous:

An unexpected error occurred. Something may be wrong with ww.wp.xz.cn or this server’s configuration. If you continue to have problems, please try the support forums.

Try again

The test code for this is a file named “ballots.php in a directory named “ballots.php” with the following stuff:

<?php
/*
Plugin Name: Ballots
Plugin URI: http://greatervoice.org/wp-plugins/ballots
Description: A polling system with user permanent ballots.
Version: 1.0
Author: Michael Coburn
Author URI: http://greatervoice.org
License: GPLv2
*/

/*
Copyright 2013  Michael Coburn  (email : [email protected]) 

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2, as
published by the Free Software Foundation.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

global $wpdb;
require_once(ABSPATH . 'wp-admin/includes/upgrade.php');

// thats all folks
?>

The actual “ballots” plugin has a lot of stuff in it. But it takes only this one line to make the system puke.

http://ww.wp.xz.cn/extend/plugins/custom-post-type-maker/