Ext.Loader.setConfig({
    enabled: true,
    disableCaching: false,
    paths: {
        GeoExt: "../../src/GeoExt",
        Ext: "http://cdn.sencha.io/ext-4.1.0-gpl/src"
    }
});

Ext.Loader.setConfig({
    enabled: true,
    disableCaching: false,
    paths: {
        GeoExt: "../../src/GeoExt",
        Ext: "http://cdn.sencha.com/ext/gpl/4.2.1/src"
    }
});

Upgrade loader to point to Ext 4.2.1