This is a result of the file being inaccessible. Sometimes this is due to .htaccess restrictions/conflicts created by the configuration of your hosting server vs your /includes/.htaccess file which is designed to prevent access to PHP files by unauthorized users. You could try temporarily renaming this file to htaccess_disabled and then if the problem is resolved, work with your hosting company to find other ways of protecting your files from unauthorized access. This will be unique to your hosting environment.
Sometimes it's due to having bad parameters in your configure.php file. But, since you're not willing to disclose a URL, there's little I can do to help further.
Check your <base href="xxxxxxxxxx" /> setting from View Source. Then check your stylesheet links. Then combine them in your browser URL and attempt to load just the stylesheet. Then deal with solving the errors that appear.
Again, your server errorlog should tell you more.
And ask your hosting company for assistance -- they should be intimately familiar with the security restrictions they're imposing on all their users.




