PHP Fatal error: Mage_{mymodule}_Helper_Data not found – Magento

I have created my own shipping method with a custom module.
I have tested it on my staging copy of my website and it works perfectly.
But for some reason, the same code doesnt work on my production website.

The error that I found is:

“PHP Fatal error: Class ‘Mage_Ship_Helper_Data’ not found in /var/www/html/app/Mage.php on line 549,”

The worse is that I dont use any helper in my module. I have created it only to respect the normal flow of magento modules.

This is a snapshot of my config.xml

 <global>
    <helpers>
        <ship>
            <class>Excellence_Ship_Helper</class>
        </ship>
    </helpers>
</global>

And this is my helper Data.php file: (as you can see, very simple)

class Excellence_Ship_Helper_Data extends Mage_Core_Helper_Abstract
{

}

I have refresh the Magento Cache, I have deleted the Helper block on my config.xml and refresh again the cache but the problem persist.