Michael, this seems to be a problem on my plugin’s as well as your theme’s side, which places </h3><div class="dbx-content"> after the widget title. Notice the final <div>, which is used for wrapping widget’s content.

The problem is that my plugin tries to hide the default widget title from being displayed inside a tabbed widget, because it is already displayed in the tab.

You should be able to fix the problem by selecting ‘Show widget title’ next to the widget title under the Tabbed Widgets settings, and adding the following CSS at the end of your theme’s style.css to hide the widget title:

#sidebar-right .tabbed-widget-item .dbx-handle { display:none; }