too long

I have copied app/code/core/Mage/Checkout/controllers/OnepageController.php to app/code/local/Mage/Checkout/controllers/OnepageController.php and overrided one function. I have also refreshed caches, but overrided controller is not called, instead original controller is called.

Why isn't my override working? I have done same kind of override for other core files and that worked well.

1. Is compilation turned off?

2. Try creating your own controller to overriding a core controller instead of copying and editing a Magento core file.

http://www.magentocommerce.com/wiki/5_-_modules_and_development/0_-_module_development_in_magento/how_to_overload_a_controller

See also: How can I override a Magento controller?