Try to require every ST element that you use in your app.
* Note that the requires must be out of the "launch" function.
Code:

Code:
Ext.application({ 
    name:'MyApp', 
    models:['User','Group'], 
    stores:['Users'],
    controllers:['Users'],
    views:['Main','ShowUser'], 
    requires: [
        'MyApp.view.LogoImage',
        'MyApp.view.LinkButton',
        'Ext.form.Panel',
        'Ext.field.Text',
        'Ext.field.Password',
        'Ext.Button',
        'Ext.Img',
        'Ext.Label'
    ], 
    launch:function(){Ext.create('MyApp.view.Main');}
});
Code:



Cheers!