Matrin,

Thank you for the quick reply. I should have chosen my words more carefully.
You're right. MSXML will produce a warning if you validate an XML document
that contains a namespace not linked to a schema. But you need to use the
validate method (IXMLDOMDocument2 object in C++) to get this behavior.
Using the load method will perform a 'lax' validation, and won't pick it
up.

Unfortunately I'm still fighting my issue. In my XML documents there are 
multiple
namespaces. The lowest level namespace appears to work just fine. It is 
first namespace declared in each document, and is linked to a schema that all 
XML documents must abide by. If I try to change the namespace so  that it 
doesn’t matchup with the XMLSchemaCache (i.e. as explained in my first post), 
I get the correct errors. Any namespace declared after the base however 
doesn’t seem to work. It follows the same behavior as explained in my first 
post.

It has to be something with the changes to MSXML 6.0 I'll keep fighting the 
fight and let you know what I find.

Thanks!