Clicking on the link to a category produces a Page Not Found error.
You can see it in action here: http://www.webiforum.com/en/on-demand/
Click on any of the categories. They are all populated and should show results.
Also, in the backend when I go to Event Categories I see all of the categories I created which is normal. However, when I look at the database table (prefix)_em_categories I see only 1 category called Uncategorized. And in the table (prefix)_em_events I checked the field event_category_id, and it says 'NULL' for all of the events.