I discovered something which means I have a little update to my situation:

First a little explanation about our website's setup. It is kind of special:
The domain ungerneonline.dk is our "main domain".
The domain ungeronline.dk points to a subfolder in ungerneonline.dk called ungeronline.

This means that you can access the same page by typing

http://www.ungerneonline.dk/ungeronline/editor.asp and
http://www.ungeronline.dk/editor.asp

It is the exact same file being executed in these two urls. What I discovered, however, is that when I load it through the first url it loads very fast and when I load it through the second url it loads very slow. It looks like the editor has some kind of problem with a domain pointing to anything else than the root folder on the domain.

Why is this the case and what can be done to make it load faster?