XDesktopPeer.launch contains:

        boolean result = gnome_url_show(uriByteArray);
        if (!result) {
            throw new IOException("Failed to show URI:" + uri);
        }

This tells you what the URI was, but not why it failed to launch:

java.io.IOException: Failed to show URI:file:/home/jglick/browsefile
        at sun.awt.X11.XDesktopPeer.launch(XDesktopPeer.java:75)
        at sun.awt.X11.XDesktopPeer.open(XDesktopPeer.java:43)
        at java.awt.Desktop.open(Desktop.java:254)

Thus it is not really possible to diagnose the problem. (In the above case, 'gnome-open file:/home/jglick/browsefile' works fine.)