Hi,
Happy new year! Thanks for your timely replies. Sorry I didn't respond any sooner. Forgot to set a notification on this post.
I tried to rule out all options and did a clean install of DNN and AS. I still get the error. I think I now can safely rule out any settings in my own installation. I included an image of the error I get in Firebug. The code i included in my first post was a bit messy.
I think the main difference between your setup and mine is I'm living in the Netherlands. The code file in which the error occurs has an Extension EN-US. Is it possible that the wrong codefile is selected for my region?
Kind regards,
Jeroen