Custom validation is not being called on production server but works on localhost

[eluser]vanquish[/eluser]
Nope, when I change the casing from my_ to MY_ it's still ignored and the echo never shows. It's like the file is invisible to CodeIgniter - no error messages or anything. When I add the line to explicitly load it: $this->load->library('my_form_validation'); I get a "404 File not found" error.