Hi Hans, I am not Joris but I am having the exact same issue and it happens with any of the objects I have attempted to download and import from:

http://www.sweethome3d.com/importModels.jsp

You can start with the very first spiral stair case.

I am on a Mac running Mountain Lion 10.8.1

Thanks ...

Hello, I am having the exact same issue as the OP. Once I hit "NEXT" the Import Wizard places image of the file I am attempting to import off-center on the views screen and completely locks up.

I would post a screen grab but..
1. I don't know how. :)
2. It would look exactly like the OPs.

Here is ...