Why are spurious SAX warnings appearing in my compilation?

Why are spurious SAX warnings appearing in my compilation?

I have a modest-sized multi-project solution written in C# which I am
developing using Microsoft Visual Studio 2010 on Windows XP. In the last
few days it has taken to reporting scores of warnings like the following:-
At least one of the arguments for 'ISAXXMLReader.getBaseURL' cannot be
marshaled by the runtime marshaler. Such arguments will therefore be
passed as a pointer and may require unsafe code to manipulate.
Similar warnings are produced for ISAXLocator, ISAXAttributes,
ISAXXMLFilter, and other apparently SAX related classes. I'm not using XML
at all anywhere in the project.
While this isn't a crippling problem, genuine warnings are getting lost in
the noise.
Does anyone know what the problem is, and what I can do about it?