Can't access WP functions in cron even though wp-load.php included

I have a file I have created to be run through a cron, but unfortunately, it can't seem to find some functions. wp-load.php is required, but when i try to access a few functions, including wp_create_category and wp_category_exists, I get back undefined for them. This is using the default wp-cron.php page, so I'm not sure what's wrong. Am I missing something about using crons with Wordpress?

via Chebli Mohamed