Great question, Christina!
It definitely looks like something odd is going on with your calendar installation as a whole. Do you notice that the event from last November is in your upcoming events list?
First, I’d recommend that you try flushing your permalinks. To do that, simply go to the permalinks settings page and click save. That should refresh them all.
Once that’s done, check out the event page and see if it looks better. If not, your best bet it to try to figure out if your theme or another plugin is conflicting with one of ours. The easiest way to do that is to deactivate all other plugins, switch to a default WP theme linke Twenty Twelve, and then start reactivating things one by one until you figure out if there’s one in particular that the behavior is linked to.
Please give that a shot and let me know how it goes. 🙂