>1. All the previous days I observed the problem but today the behaviour is normal (well..., what I think should be normal): the parameter tdDate is unchanged. I am using the same program without changes, so has something changed in your servers?

Yes, because I changed the WSDL file to have xsd:date instead of xsd:datetime.

>What is the logical reason for that? Why a VFP client is different than a VB client regarding this subject?

I've been told its regarding the COM type library mapping which is different from VFP to something else I guess.