You deliver a Silverlight module that uses WCF Services to a production server. It works great on your machine, but when you run it in production, you get an error every time you call out to a WCF service.
The issue may be in the ServiceReference.Config file. In the <System.serviceModel> section, in the <client> section, you will see endpoints for every service. Change the 'address' of these to the endpoints that you use in production, recompile, and deliver the module.