Programming a web service client against a .NET server is a lot harder than it needs to be.
The request to such a service must be absolutely correct, even in the areas where XML itself allows a lot of slack. It isn't enough to have the proper type and construction of the data parameters in the right order, they must be named correctly. Note that services written in less-stringent languages (such as, say, Perl) are good about the "be liberal in what you accept" mentality. The SOAP interface to this journal system, for example, is an excellent illustration of this.
The MapPoint.NET service is not.