Comment on WordPress Widgets Tutorial by SEO Dave.
When you add your first widget to a sidebar all the default widgets for that sidebar vanish, that’s normal and a feature of WordPress core. The widget menu is designed so you can add only the widgets you want and not the ones the theme developer thinks you should use. If this is the problem after adding your first widget re-add the default widgets you like as you did the first one, build the sidebars exactly how you want them.
I can only add the GAT widgets once.
The GAT widgets are currently (Stallion 6.0.1) coded with old WordPress code (nothing wrong with the code, just lacks newer features like options and multiwidget capability). This code lacks multiwidget capabilities, you can only add a widget once. For almost all the GAT widgets this isn’t a problem, but for a few might be nice to have the option to add the widget two or more times.
In Stallion 6.1 I’ve updated the widget code so in a future release (not 6.1) can add options to some of the GAT widgets which may include multiwidget capabilities. For example the comments widget would work better with the option to set the number of comments, currently limited to either 12 or 18 comments. Next update will probably incorporate thumbnails into some of the widgets.