Listings: 404 – Article Not Found

Hey there,
Geodirectory used to work fine for me, but all of a sudden, I am getting 404 errors if I click on ANY listing!
http://eventlocations-baden.de
It’s the same on the home page and on the search-page – Listings are displayed, but if xou click on them you get a 404.

I am using GD 1.6.2 and disabled all other plugins except for:
GeoDirectory Advance Search Filters
GeoDirectory Custom Post Types
GeoDirectory Marker Cluster
GeoDirectory Payment Manager

Cache is cleared.
Testing in safari and chrome.
Please help me!