Bing Maps WPF Control: map tiles get scrambled, why?

Dsungaro
1
Reputation point
I've got the Bing maps WPF control included into my Windows Forms app (via ElementHost) and when viewing the map (also in Design Preview), the map tiles are scrambled. I'm behind a company firewall and accessing the Internet without firewall is not an option.
What is the cause for the scrambled tiles?