I'm having trouble getting the XML plugin to use an XML catalog to locate the schema referenced by my document. Can anybody help? Assuming all three documents (document to be edited, referenced schema and XML catalog) are in the same folder, I would expect the following to work:

root element of edited document:
<Ace
xmlns="http://www.birdstep.com/xml/schemas/acedb"
xsi:schemaLocation="http://www.birdstep.com/xml/schemas/acedb http://www.birdstep.com/xml/schemas/acedb.xsd"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>

catalog element in catalog document:
<catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog" prefer="public">
<public publicId="http://www.birdstep.com/xml/schemas/acedb" uri="acedb.xsd"/>
</catalog>

If http://www.birdstep.com/xml/schemas/acedb.xsd is not available, I would expect the editor to look up http://www.birdstep.com/xml/schemas/acedb in the catalog and so find acedb.xsd in the current folder.

What actually happens is that the editor returns HTTP 403. I've tried endless variations on the above setup, all with no luck...

PS. I have added my catalog to the list of catalogs in the XML plug-in's options.