XML validation bug in 2003 .NET studio

[Dennis M]

I was wondering anyone else has seen this.

I've created a schema where I have a base element type which is
abstract. From it derived three other types which have additional
attributes/child elements.

When I create an XML file and specify that the element is actually the
deriving type using xsi:type attribute I get error message.

If I don't specify additional attributes defined as required in the
deriving type, I get the message: "The required attribute 'xxx' is
missing. An error occured at , (5, 4)."

But if I specify the attributes it says are missing, then I get the
following error: "Could not find any attribute 'xxx' of element 'yyy'

So the file never validates. Is this a bug? If it is, is it known?
If it is not, anyone know what I am missing? I've done very similar
thing using XMLSPY and had no problems, but I don't have a copy at
home, so I am trying to use visual studio.

Thanks,

-- Dennis