SourceID.NET --another Server Error in '/idp' Application

I’m getting an error, when computing the signature of the response to the
request of authentication. I think it’s related with what is written in the
reame.txt that came with the code, about how to get exclusive
canonicalization working.  In what place of the machine.config I must place
the “codeâ€, inside the <configuration>,  or inside another element?

The error message that I get is this:



Server Error in '/liberty' Application.
----------------------------------------------------------------------------
----

Could not create the XML transformation identified by the URI
http://www.w3.org/2001/10/xml-exc-c14n#.
Description: An unhandled exception occurred during the execution of the
current web request. Please review the stack trace for more information
about the error and where it originated in the code.

Exception Details: System.Security.Cryptography.CryptographicException:
Could not create the XML transformation identified by the URI
http://www.w3.org/2001/10/xml-exc-c14n#.

Source Error:


Line 373:            sx.AddReference(reference);
Line 374:
Line 375:            sx.ComputeSignature();
Line 376:
Line 377:            if (assertion != null)


Source File: d:\sso\sourceid\xmlutils.cs    Line: 375

Stack Trace:


[CryptographicException: Could not create the XML transformation identified
by the URI http://www.w3.org/2001/10/xml-exc-c14n#.]
   System.Security.Cryptography.Xml.SignedXml.ComputeSignature()
   SourceId.XmlUtils.SignResponse(ResponseAbstractType response,
AsymmetricAlgorithm key, XmlSerializer serializer) in
d:\sso\sourceid\xmlutils.cs:375
   SourceId.HttpHandlers.Authenticator.HandleAuthReturnToSP(HttpContext
context, AuthnRequestType authn_req, ProviderDirectory dir, SPDescriptorType
sp) in D:\sso\SourceId\HttpHandlers\Authenticator.cs:470
   SourceId.HttpHandlers.Authenticator.HandleAppAuthenticated(HttpContext
context, AuthnRequestType authn_req, Object uid, ProviderDirectory dir,
SPDescriptorType sp) in D:\sso\SourceId\HttpHandlers\Authenticator.cs:263
   SourceId.HttpHandlers.Authenticator.Process(HttpContext context) in
D:\sso\SourceId\HttpHandlers\Authenticator.cs:89
   liberty.LogonPost.Page_Load(Object sender, EventArgs e) in
c:\inetpub\wwwroot\liberty\LogonPost.aspx.cs:114
   System.Web.UI.Control.OnLoad(EventArgs e)
   System.Web.UI.Control.LoadRecursive()
   System.Web.UI.Page.ProcessRequestMain()

----------------------------------------------------------------------------
----
Version Information: Microsoft .NET Framework Version:1.1.4322.573; ASP.NET
Version:1.1.4322.573

Thanks,
Paulo Ruivo