Well, the code is not actually breaking.  Everything compiles just
fine.  So, hopefully, snippets will add some insight...

In my main class, I have:

DefaultListModel model = new DefaultListModel();
JList fileList = new JList(model);
fileList.setSelectedIndex(0);
fileList.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
fileList.setLayoutOrientation(JList.VERTICAL);
fileList.addListSelectionListener(new FileListListener());

I then add elements to my list with code similar to this:

for(int i = 0; i < 6; i++)
     model.add(i,"ListElement");

And my listener class looks like this:

protected class FileListListener implements ListSelectionListener
{
    public void valueChanged(ListSelectionEvent e)
    {
        if(e.getValueIsAdjusting())
            return;

        System.out.println("Index: " + fileList.getSelectedIndex());
    }
}

So, everything builds just fine and the GUI looks great.  Every time I
click on a list element, it prints Index: -1.  This tells me that the
listener is set up fine, but that something is not in place so my JList
knows what is selected.

Does this help?

Thanks,
Ben