Gxt combo box selection arrow is not properly aligned in firefox and safari

I am using Gxt-2.2.3's combox box, when it is rendering in IE7 there is no problem with the alignment, but when it comes to Firefox-4.0.1 have got some selection arrow alignment issues as follows.

By ran the application is firebug mode , came to know that there some default style is applied to this div 'element.style' with value 'padding-left:80px'. So can any one suggest me why this incompatibility in browsers, and how do i override this style.

code:

private ComboBox<TestModel> comboModel = new ComboBox<TestModel>();

  comboModel.setFieldLabel(wrapAlignmentSpan("State"));
    ListStore<TestModel> store = new ListStore<TestModel>();
    store.add(getModels(new ArrayList<TestModel>()));
    comboModel.setDisplayField(TestModel.STATE);
    comboModel.setValueField(TestModel.STATE);
    comboModel.setLabelStyle("font-weight:bold;width:120");
    comboModel.setWidth(100);
    comboModel.setStore(store);

and finally i am adding this one to 'FormPanel' as follows:

     mainPanel.add(comboModel);

Thanks in advance.