Accessing WebServices methods fails on instantiating object

Question

Hi,

I'm using C# to invoke some webservices operations. I create the client like so:

EnterpriseSoapPortClient clientEnterprise = new EnterpriseSoapPortClient();

And after this, I invoke the method like this:

clientEnterprise.GetSites()

The error I get is this:

WSDLOperation: Instantiating the dispatch object for method GetSites failed

These services are hosted in a Windows Server 2003 using IIS 6.0 and with anonymous access activated. Any ideas on what this problem could be?

Thanks in advance