Set base_url in Settings.php

When filtering events by terms or event type with the filter seen above the month, week or day view the filter gets stuck (you cannot change the values anymore) and the URL messes up by repeating like the following example. Spaces are added to show the part that is "repeated" every time the filter is "used":

http://example.com/ event/2007/05/03/ event/2007/05/03/month/ event/2007/05/03/ event/2007/ event/2007/05/03/ event/2007/ event/2007/05/03/event/event/ event/2007/05/03/ event/2007/ event/2007/05/03/ event/2007/ event/2007/05/03/event/2007/all

This is because the value of the action attribute in the filter form is not set properly. I tried to narrow it down a little bit more but haven't really got any insight. (Where is the ???['#action'] value set?)