Ray - according to the client, the test showed the referer properly. I'm checking to make sure that the test was done from the same computer as the original order.
Here's an interesting thought. I could recommend to my client that he issue this customer a $10 credit, in return for which the customer would place another order (there are items that this would cover). If that order goes through OK, then we know that either a) he didn't use the same computer as before, or b) he did, and the failure was at the server side of things.
Meanwhile, I'm checking with the host for their server logs....