Recently, when I was working on a project that contained a WCF service that I was having problems with. i deleted the service, but forgot the delete the reference to the service within my web.config file. Funny thing though, Visual Studio will let this compile (if you have two independent references to the same service, for configuration) The thing is, though, when you try to consume the service, you will come upon errors included the that of which you can see at the top of this article.
The solution to this was easy, just delete the old reference, and ensure there is only a single reference to the service in question. A simple solution to a problem that could have easily been avoided when I replaced my service.
Just something to watch out for, if you come upon it, you may want to check your service declarations within your web.config and make sure you’re declaring the reference, only once.