Why would "Format" Context Menu Not Work for XML?

[tomwheeler]

I have a custom project type for an application based on the NetBeans
IDE 6.7.1. The project contains an XML file and double-clicking it
opens it in the editor, complete with syntax highlighting and the
other features I expect from the IDE.

The context menu contains the "Format (Ctrl+Shift+F)" item. Although
it's enabled, invoking it by either the menu item or keybinding has no
effect -- the document is never formatted. I can repeat this for any
XML file in the application, whether I open it from the project tab or
through Favorites.

Any ideas on what I need to do to get this to work? My guess would be
to enable some module, though it's not clear which one.

--
Tom Wheeler
http://www.tomwheeler.com/