Thanks for the response (you're up early!). Everything is loading fine from what firebug says, with the exception of the gif files (border, tabfirst and tablast). These were the only items I didn't copy over from the example code before I started my adaptation. The css and js files look like they're loading fine (inspected the response). My index.html has the tag for the css file (ext-all.css and GroupTabPanel.css) , my view (which is defined within my main controller) is where I have listed the Ext.ux.GroupTabPanel as a required file. (it's only within my view - did I need to add it elsewhere? seems to load fine).
I've taken a few steps back from my adaptation to try to pinpoint where something is amiss, but luck. Nobody else having problems? I saw ppl posting questions about earlier versions of ExtJS so there must be something I'm doing wrong.

Code:
{
            xtype: 'grouptabpanel',
            activeGroup: 0,
            items: [
               {
                mainItem: 0,
                items: [{
                    title: 'Help Pages',  
                    //border: false,
                    xtype: 'panel',
                    items:[{title:'hi'}],
                    height: null
                },{
                    title: 'Using the Tool',  
                    //border: false,
                    xtype: 'gridportlet',
                    height: null
                },{
                    title: 'How To...',
                    style: 'padding: 10px;',
                    border: false,
                    layout: 'fit',
                    items: [{
                        xtype: 'tabpanel',
                        activeTab: 1,
                        items: [{
                            title: 'Nested Tabs',
                            html: '<p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Sed metus nibh, '+
    'sodales a, porta at, vulputate eget, dui. Pellentesque ut nisl. Maecenas tortor turpis, interdum non, sodales '+
    'non, iaculis ac, lacus. Vestibulum auctor, tortor quis iaculis malesuada, libero lectus bibendum purus, sit amet '+
    'tincidunt quam turpis vel lacus. In pellentesque nisl non sem. Suspendisse nunc sem, pretium eget, cursus a, fringilla.</p>'
                        }]  
                    }]  
                },{
                    xtype: 'portalpanel',
                    title: 'FAQ',
                    tabTip: 'Dashboard tabtip',
                    border: false,
                    items: [{
                        flex: 1,
                        items: [{
                            title: 'Portlet 1',
                            html: '<div class="portlet-content"><p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Sed metus nibh, '+
    'sodales a, porta at, vulputate eget, dui. Pellentesque ut nisl. Maecenas tortor turpis, interdum non, sodales '+
    'non, iaculis ac, lacus. Vestibulum auctor, tortor quis iaculis malesuada, libero lectus bibendum purus, sit amet '+
    'tincidunt quam turpis vel lacus. In pellentesque nisl non sem. Suspendisse nunc sem, pretium eget, cursus a, fringilla.</p></div>'
                        },{
                            
                            title: 'Stock Portlet',
                            items: {
                                xtype: 'chartportlet'
                            }
                        },{
                            title: 'Portlet 2',
                            html: '<div class="portlet-content"><p>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Sed metus nibh, '+
    'sodales a, porta at, vulputate eget, dui. Pellentesque ut nisl. Maecenas tortor turpis, interdum non, sodales '+
    'non, iaculis ac, lacus. Vestibulum auctor, tortor quis iaculis malesuada, libero lectus bibendum purus, sit amet '+
    'tincidunt quam turpis vel lacus. In pellentesque nisl non sem. Suspendisse nunc sem, pretium eget, cursus a, fringilla.</p></div>'
                        }]
                    }]                  
                }]
            }
            , 
               { 
                items: [{
                    title: 'Quick Reference',
                    style: 'padding: 10px;',
                    items:[{
                        xtype:'form',// since we are not using the default 'panel' xtype, we must specify it
                        layout: 'anchor',
                        defaults: {
                           anchor: '100%'
                        },


                         // The fields
                        defaultType: 'textfield',
                        items: [{
                         fieldLabel: 'First Name',
                         name: 'first',
                         allowBlank: false
                         },{
                         fieldLabel: 'Last Name',
                         name: 'last',
                         allowBlank: false
                        }],


                    // Reset and Submit buttons
                    buttons: [{
                       text: 'Test'    
                       
                    }]
                        }]
                }, {
                    title: 'Lookup',
                    style: 'padding: 10px;',
                    border: false,
                    items:{
                            xtype: 'form', // since we are not using the default 'panel' xtype, we must specify it
                            buttons: [{text: 'Save'},{text: 'Cancel'}]
                        }
                }]
            }]
        
    }