DocumentBuilder.parse() returns [#Document: null]

I've written some XML parsing code that works well on my Tomcat 6 /
JRE 1.5 development server

, but fails on my Web Logic 8 / JRE 1.5
server.

This is the code:
// Create a builder factory
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setValidating(validating);

// Create the builder and set error handler class
DocumentBuilder builder = factory.newDocumentBuilder();
builder.setErrorHandler(new BasicErrHandler());

// Create the doc by parsing the file
Document doc = builder.parse(new File(filename));


Things are fine on my Tomcat server, but on the Web Logic server, the
Document object "doc" is a bunch of empty nodes, and has a very
strange toString() value of "[# document

: null]".

I've searched high and low, and the only reference to this I've found
was solved by somebody who said "well it turns out that a
mis-configuration of my fire-wall blocked attempts to call local
urls...".

....But why would DocumentBuilder.parse() need to call local URLs? The
XML file, although it contains a DTD, is just a standard hierarchical
collection of TextNodes.

Has anybody ever seen this?


Thank you... --Jack.