Joe,
Concentrating on the 9.3.1 boxes, I notice that I only get the XML error when there are records to be pulled. When I make the call to the "standby" unit, I do not get the error - the record returns empty. But when I make the call to the "active" unit (which has persistent connections), I get the XML error.
I have made sure that my Visual Studio is up to date on patches, but that did not help either.
I have attached the detail of the XML error to the post. If you could glance at it, I would be much obliged.