Cannot install InDesign Server CS4: Win 2003 x64

One of my customers has just purchased InDesign Server CS4 (Single Instance, Premium License) and I'm trying to install build 525 on Windows Server 2003 Enterprise Edition x64. I select the default 'Easy/Recommended' installation settings and the installer runs through, but then displays the message below. I've tried installing to different directories but hit the same error every time.

When I select 'Next' the installer lists the following products and components have been successfully installed:

• Adobe InDesign CS4 Server
• ID Server service files
• ID Server components
• ID Server service files (x64)

However, it doesn't appear to have installed correctly, as if I start the InDesign Server service and then execute the following test script nothing happens:

#target indesignserver;

//HelloWorld.jsx

//Create a new document.

    var myDocument = app.documents.add();

//Get a reference to the first page.

    var myPage = myDocument.pages.item(0);

//Create a text frame.

    var myTextFrame = myPage.textFrames.add();

//Specify the size and shape of the text frame.

    myTextFrame.geometricBounds = ["6p0", "6p0", "18p0", "18p0"];

//Enter text in the text frame.

    myTextFrame.contents = "Hello World!";

//Save the document (fill in a valid file path).

    myDocument.save(new File("/e/HelloWorld.indd"));

//Close the document.

//Close the document.

    app.documents.item(0).close();

Any ideas?