If your OneStepCheckout page is a completely blank page, with correct header and footer design but nothing in the middle, it means Magento can't find the OneStepCheckout template and layout files.
This is usually a problem with Magento 1.3 and below. The reason for this, is that OneStepCheckout is located in the "default/default" folder. If your active package is '''not default''', Magento will not find the OneStepCheckout files.
To solve this, you must upload/copy the OneStepCheckout templates and layout files from "default/default" to "yourpackage/default".
So if your custom package is called "mypackage", you need to copy the following files from
Then, refresh your cache and Magento should pick up the templates and use them automatically.
NB: This is not an issue with Magento 1.4 and above, because they use a "base" package which always will be inherited.