This error occurs if your IP address is not activated at ABK-Soft side.
Create a ticket for them at http://members.abk-soft.com/
, providing your server's IP adress and asking to activate 3D City for you.
Also, there are couple of things you need to check before running it:
1. Make sure your site has no HTTP Basic access protection. This is done often at the development stage to preserve search engines from early indexing your site. If your site has this protection, you most probably will get "Q3D file corrupt" error (well, normally, if you can get to your site's home page without any user/password requests - you are ok in this regard.
2. When you try to load it in IE - your browser must have protected mode DISABLED. Check this in IE properties dialog box, Security tab - "Enable protected mode..." must be UN-checked. You need to advise this to all your users.http://3d-city.net/img/edit.jpg
I also run 3DCity in Chrome browser. Before that you (and your users) need to install IETab extention from http://www.ietab.net