I'm running ZC 1.37 and i've had this same problem with paypal forever. This problem seems to stem from setting up paypal ipn to accept credit cards, which for some reason turns off the automatic redirect feature. So, when a credit card order is completed, if the customer doesn't click the link back to your site then the order details are not sent back. Paypal says they are working on the issue, but I don't hold my breath with them.

Looking for mods to fix this or to be able to turn a customers shopping cart into an order manually without having to re-enter any information. I have the Admin Login as Customer mod installed and it does allow me to login and see what's in a cart, but I can't get the "place an order" function to work. Next up; try Super Orders.