Ext Version: extjs 4.1.0 Final
Browsers: Firefox and Chrome (probably the others as well)
Problem:

I'm not exactly sure what is happening, but no matter where I put a datefield, when I click its corresponding datepicker, the datefield disappears, the datepicker calendar shows up in an unexpected place, and the rest of the layout of the page gets totally distorted in weird ways. Even in the simple scenario:

Code:
Ext.define("MyCompany.Viewport", {
    extend: 'Ext.panel.Panel',
    layout: 'fit',
    items: [
      {
           xtype: 'datefield',
           fieldLabel: 'Testing Datefield',
           format: 'mm/dd/YYYY'
       }
});
this issue happens. See attached screenshots of before/after click. What is happening?

Thanks,
Jeff

Datefield_Before.pngDatefield_After.png