ExtJS 4.0.2a Window Header Styling

So we've "updgraded" to ExtJS 4.0.2a.

I'm trying to create a simple window with a fieldset that has three inputs, and hides on close (as I've done with 4.0.1).

addModWindow = Ext.create('Ext.Window',{
    title: 'Title',
    frame: true,
    width: 500,
    height: 200,
    closable: true,
    closeAction: 'hide',
    layout: {
        type: 'fit',
        align: 'center'
    },
    defaults: {
        bodyPadding: 4
    },
    resizable: false,
    items: [{
        xtype: 'fieldset',
        labelWidth: 75,
        title: 'Rule Val开发者_运维问答ues',
        collapsible: false,
        defaults: {
            anchor: '100%'
        },
        width: 490,
        items: [typeComboBox,ruleTextBox,notesTextArea]
    }]
});

typeComboBox, ruleTextBox, notesTextArea are defined just above this block and don't seem to have any issues (as I've removed the items and still have this same problem).

When the window is shown, the window body and close box render correctly, but the window's header is now transparent and has minimal styling (font-family). I've attached the screen caps from FF4, IE8, and Chrome.

Has anyone else seen this problem and found how to get rid of the transparency? In IE8 when you move the window, you can see the correct styling of the window header, which leads me to think that the css classes aren't getting applied correctly.

In FF4:

In IE8:

IE8 Move:

In Chrome: