If you are getting a "Access denied" message when accessing the OneStepCheckout configuration in Magento administration, please do the following:
- Go to System -> Cache Management and do a "Refresh" on all cache
- Logout of your Magento administration
- Log back in and try to access OneStepCheckout configuration (System -> Configuration -> OneStepCheckout)
Then it should work as expected. If you are still getting an "Access denied" message, please contact us.
If none of the above works, try going to System -> Users and roles -> Roles, and try to re-save the administration role and then logout and back in again.