When adding this plugin and going to "home" (the front page) I only get to see the widgets above this plugin in the widget area + the category list from this plugin.
Only when I click on "Category" does the rest of the widgets in the area become visible.
My first suspect was some kind of caching, but unfortunately the test site I ran this on has no caching and very few plugins.
Likely a missing end tag of some sort...
Maybe due to incompatibility with WP 3.5.1 or the 2012-theme. Have not tested with other themes of WP versions.