My wordpress site goes blank when I edit wp-config

[admin]

I'm trying to edit my

wp-config

file so my wordpress information is hidden on my site. When I edit it, the entire site goes blank. When I go to the wordpress dashboard I get the following error message:

<blockquote>
ERROR:The themes directory is either empty or doesn’t exist. Please check your installation
</blockquote>

All I've added (just before the last line [something about require_once]) is:

define('WP_CONTENT_FOLDERNAME', 'media');
define('WP_CONTENT_DIR', ABSPATH . WP_CONTENT_FOLDERNAME );
define('WP_CONTENT_URL', 'http://brightpixelstudios.com/'.WP_CONTENT_FOLDERNAME); 
define('WP_PLUGIN_DIR', WP_CONTENT_DIR . '/plugins' );
define('WP_PLUGIN_URL', WP_CONTENT_URL.'/plugins');

Any ideas what might be causing the problem? It could be worth mentioning that I have both a

.com

and a

.co.uk

name for the same site.

Any advice would be appreciated.