menubar,scroll vibration

hi,
In my project I have a menubar , panels with scroll bar
when make any action that change any menu item enabled flag , the scroll bars in panel vibrate
I notice that with only size full panels
this is a sampl link I uploaded
http://tom7-calender.rhcloud.com/MenuBarTest
and this my code
package com.example.menubartest;

import java.util.List;

import com.vaadin.Application;
import com.vaadin.ui.Button;
import com.vaadin.ui.Button.ClickEvent;
import com.vaadin.ui.Label;
import com.vaadin.ui.MenuBar;
import com.vaadin.ui.MenuBar.MenuItem;
import com.vaadin.ui.Panel;
import com.vaadin.ui.TextArea;
import com.vaadin.ui.Window;

public class MenubartestApplication extends Application {
@Override
public void init() {
Window mainWindow = new Window(“Menubartest Application”);
final MenuBar menuBar = new MenuBar();
for (int i = 0; i < 5; i++) {
MenuItem main = menuBar.addItem(“” + i, null);
for (int j = 0; j < 5; j++) {
main.addItem(j + “”, null);
}
}
mainWindow.addComponent(menuBar);
for (int i = 0; i < 3; i++) {

        Panel panel = new Panel();
        panel.setSizeFull();
        panel.setScrollable(true);
        TextArea area = new TextArea();
        area.setWidth(300, Panel.UNITS_PIXELS);
        area.setHeight(100, Panel.UNITS_PIXELS);
        ;
        panel.addComponent(area);
        mainWindow.addComponent(panel);
    }
    Label label = new Label("Hello Vaadin user");
    mainWindow.addComponent(new Button("tes", new Button.ClickListener() {

        public void buttonClick(ClickEvent event) {
            List<MenuItem> list = menuBar.getItems();
            for (MenuItem menuItem : list) {
                menuItem.setEnabled(!menuItem.isEnabled());
            }

        }
    }));
    setMainWindow(mainWindow);
    mainWindow.getContent().setSizeFull();
    setTheme("menubartesttheme");
}

}

how can i prevent that vibration in scroll??