Magento Shipping Estimator - Not Working (empty results)

Not sure when this will happen, but I have an estimated shipping amount on the cart page that is not working. After filling in the information and clicking "Get a quote", the page reloads, but the delivery methods are not displayed to the user ... it is as if the form were submitted with empty values. The form indicates:

checkout/cart/estimatePost

      

        
        
        
      

    

The content of which (in app / code / core / Mage / Checkout / controllers / CartController.php):

    public function estimatePostAction()
{       
    $country    = (string) $this->getRequest()->getParam('country_id');
    $postcode   = (string) $this->getRequest()->getParam('estimate_postcode');
    $city       = (string) $this->getRequest()->getParam('estimate_city');
    $regionId   = (string) $this->getRequest()->getParam('region_id');
    $region     = (string) $this->getRequest()->getParam('region');

    $this->_getQuote()->getShippingAddress()
        ->setCountryId($country)
        ->setCity($city)
        ->setPostcode($postcode)
        ->setRegionId($regionId)
        ->setRegion($region)
        ->setCollectShippingRates(true);

    $this->_getQuote()->save();
    $this->_goBack();
}

      

        
        
        
      

    

I added Mage :: log here to test the request:

$request = $this->getRequest()->getParams();
Mage::log($request, null, 'temp.log');

      

        
        
        
      

    

The array being registered is completely empty. No parameters even get there.

I looked at the form and it is exactly the same as the form on the development site (which works fine). So the problem is not with the form itself.

The only real logical conclusion is that another module bypasses everything. I've checked various modules for overriding CartController.php, and while there are some that do this, none of them mess around with the PostAction () method.

I'm a bit puzzled, any ideas?