LWJGL Renderer Thread Error

Question

Guys I have a trouble with jmonkeyengine. In jme3's forum I could not get any efficient help on my problem. Actually no one says what my problem is. Because I am new in lwjgl and jme3, I also do not know what happens. Simply I have created a basicGame on jmonkey which is first template as an example. Then I created its applet or webstart distros. When I run it, it throws an exception occuring between jme3 and lwjgl. And it says:

Exception in thread “LWJGL Renderer Thread” java.lang.IllegalStateException: No loader registered for type “fnt”
    at com.jme3.asset.ImplHandler.aquireLoader(ImplHandler.java:199)
    at com.jme3.asset.DesktopAssetManager.loadAsset(DesktopAssetManager.java:266)
    at com.jme3.asset.DesktopAssetManager.loadFont(DesktopAssetManager.java:365)
    at com.jme3.app.SimpleApplication.loadGuiFont(SimpleApplication.java:178)
    at com.jme3.app.SimpleApplication.initialize(SimpleApplication.java:186)
    at com.jme3.system.lwjgl.LwjglAbstractDisplay.initInThread(LwjglAbstractDisplay.java:130)
    at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:207)
    at java.lang.Thread.run(Unknown Source)

and the code of BasicGame template in jme3:

/**
 * test
 *
 * @author normenhansen
 */
public class Main extends SimpleApplication {

    public static void main(String[] args) {

        Main app = new Main();
        app.start();
    }

    @Override
    public void simpleInitApp() {
        Box b = new Box(Vector3f.ZERO, 1, 1, 1);
        Geometry geom = new Geometry("Box", b);

        Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
        mat.setColor("Color", ColorRGBA.Blue);
        geom.setMaterial(mat);

        rootNode.attachChild(geom);
    }

    @Override
    public void simpleUpdate(float tpf) {
        //TODO: add update code
    }

    @Override
    public void simpleRender(RenderManager rm) {
        //TODO: add render code
    }
}

Notes:

- BasicGame project has been built on either Linux or Windows

- Original JMonkeyEngine SDK has been used

- An example is in http://appletgame.comeze.com/ (just click on 'run-applet.html')

- File Permissions on the webpage are 755 for all files.

Is there someone who knows why I get this error and what could be done?