Have you tried with PayPal Express? I originally used PayPal Standards on an ecommerce website and ran into some "logical" problems when i was designing the pages...So was recommended to use PayPal Express (to do this just select PayPal Pro from the wizard) The you would need to do a little custom coding and remove the credit card form thats generated on the checkout form.
To be honest I did recall having a simular issue that your having originally and Im trying to remember what the reason was..once I remember will let you know.
Chris