Only Default Controller Working

Hi,

Only my default controller works. If I comment out my is_logged_in check, my default controller loads. If I do the same with any other controller, they do not work. So if I go to Welcome with log in check disabled, everything is fine. If I do log in check and get redirected to domain/auth/login, 404 page not found.

this is my .htaccess in root folder.Mod_Rewrite works because I do get 500 internal error with mistakes in .htaccess file.

Code:

RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]

My config is:

Code:

$config['base_url'] = 'http://sub.domain.com';
$config['index_page'] = '';
$config['uri_protocol']    = 'REQUEST_URI';

I've tried so many different things and nothing works. I'm at a complete loss.

Thanks for your help in advance.