Tab and Shit+Tab not being caught on the 'key' listener

When I moved the following code into a plug-in it no longer catches the tab or shift+tab key strokes.

All other keystrokes are being caught, any thoughts?

Also if I put this code not in the plug-in and instead on where I initialize my editor it catches everything, but I need to be in the plug-in for a couple reasons.

CKEDITOR.plugins.add('myPlugin',
{
    init: function (editor) {

        // Hook into to all Key events
        editor.on('key', CustomKeyEvents)
  }
});

// Custom Key Events function
function CustomKeyEvents(e) {
  alert (e.data.keyCode) ;
}

}

Thanks,
Adam