I have seen in some sites, that when you choose paypal payment method, you get redirected to a page on the left side there is credit card submission box on the right side there is paypal login for those already rregistered. but on my site when choosing paypal i get, i only paypal login page right under the box it says if u dont have a paypal account click here how to get the option i see on the other sites .
Do you offer recurring memberships with Paypal Website Payments Standart? If so, user will not be able to pay without paypal account, so CC info screen will not be available.