403 Forbidden Error for Upgrade.php

So, I decided to finally break down and see what all the talk is about with these upgrades, though the two different version possibilities confuses the heck out of me. To play it safe, I decided to start with my sandbox, wpdemo. I deleted all of the files there to start fresh and uploaded the files for WP 2.1.3 which I downloaded today.

Since I already have a database I’ve populated and been using for my sandbox, I filled in the wp-config.php file and excitedly went to start the upgrade process.

I called up the upgrade.php file and hit “Upgrade WordPress” only to receive the following error:

Forbidden
You don’t have permission to access /wpdemo/wordpress/wp-admin/upgrade.php on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.
Apache/1.3.37 Server at https://www.exit-23.net Port 80

The permissions appear to all be correct. I tried to reinstall. My old un-upgraded installations of WP appear to still be working. I can’t imagine what else might be causing this.