Problem with "Using a pre-existing subdirectory install"

I followed the instructions provided in “Using a pre-existing subdirectory install” and it worked at first, but now I just get a blank screen when I try to access the site from: wendydebeck.ca.

The site still works fine from wendydebeck.ca/wp. I noticed in the Settings-General area that the Site Address(URL) that the value mysteriously changed back to wendydebeck.ca/wp.

I tried changing it back to the root directory, but I just got “The content you are looking for is not availible (sic).”

The contents of my .htaccess file is:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /wp/
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /wp/index.php [L]
</IfModule>

# END WordPress

The content of my index.php is:

<?php
/**
 * Front to the WordPress application. This file doesn't do anything, but loads
 * wp-blog-header.php which does and tells WordPress to load the theme.
 *
 * @package WordPress
 */

/**
 * Tells WordPress to load the WordPress theme and output it.
 *
 * @var bool
 */
define('WP_USE_THEMES', true);

/** Loads the WordPress Environment and Template */
require( dirname( __FILE__ ) . 'wp/wp-blog-header.php' );

I was careful to follow the instructions exactly.