Adding a Button to a Dialog

Ok,

I've been banging my head against the wall for a few days now trying to simply add a 3rd button to a dialog I created. For the life of me, I'm clearly doing something wrong. Can anyone see why this .js file (which contains the code for the dialog) would fail ?

CKEDITOR.dialog.add( 'test', function( editor )
{
   return {
      title : 'My Dialog',
      minWidth : 400,
      minHeight : 200,
      contents : [
         {
            id : 'tab1',
            label : 'First Tab',
            title : 'First Tab',
            elements :
            [
               {
                  id : 'input1',
                  type : 'text',
                  label : 'Input 1'
               }
            ]
         }
      ],
      buttons: [
            CKEDITOR.dialog.okButton,
         
            CKEDITOR.dialog.cancelButton,
         
            {
               id: 'unique name',
               label: 'Custom Button',
               title: 'Button description',
               accessKey: 'C',
               disabled: false,
               onClick: function()
                  {
                     // code on click
                  },
            }
         ]

   };
} );

It's clearly something in 'buttons' area (due to the fact that when i remove the 'buttons : [] ' section the code suddenly works, so i'm sure the parser sees something it doesn't like in the buttons : area. In firefox I tried to figure out what fails using firebug and it claims the following line fails : Line 97 of ckeditor.js "a.dialog._.uiElementBuilders[Q.type] is undefined" but that's a bit nebulous unless i try to understand the entire application.

I'm sure it's some stupid 'syntactical' error but I'm using direct samples from ckeditor documentation (http://docs.cksource.com/FCKeditor_3.x/ ... log_System) that show the buttons: syntax so i'm at a loss. Please help !