fra_casula on "[Plugin: W3 Total Cache] Custom files doesn't work anymore"

The problem persists. It seemed fixed but the rackspace URLs now expose my document root path (ie. http://rackspacecdn.com/var/www/... that's bad!).
The W3 Total Cache engine also tries to replace the image url through the ob_callback() function on the frontend side but it builds the wrong regexps (with the full path).
So, the only way to get this done seems through placeholders but they don't work with subfolders.

This is my apache virtual host:

<VirtualHost *:80>
Alias /company/blog "/var/www/company/blog-root"
<Directory "/var/www/company/blog-root/">
AllowOverride All
Order allow,deny
Allow from All
</Directory>
</VirtualHost>

My siteurl and home options are "http://www.example.com/company/blog"

My .htaccess is:

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

What's wrong?