Naming of Controllers - any names not allowed?

I am building an application, and wanted to have one of the controllers called Resources. No matter what I try, my app will not allow me to use this name - when I try to use a link `<a href="<?php echo base_url(); ?>resources">`, I get an "Object Not Found" error instead of the page. With any of my other controllers, I have no issues. Is Resources a restricted word for controllers?