Can someone please give me an explanation of the data flow/log file creation process for PayPal Express? We're trying to troubleshoot a sporadic problem in which the order process appears to be interrupted. I don't think it's just paypal, but paypal seems to have a very good logging function so I'm hoping this will help.

For example, I have a customer who tried and failed to place an order. In the paypal log directory, I found three files for SetExpressCheckout for this order, but none of the other log files that are usually created.

We're using 1.3.9h.

Thanks,

John