Check if you have some "security" component installed on your Joomla site. It may have applied access restrictions using .htaccess files to the /media folder (and perhaps others) in Joomla, for specific tasks like downloading.

Or you have some weird redirect in your main .htaccess file for kunstzone.nl that does not match www.kunstzone.nl. That would explain the redirect to the login page. Of course it could also be the "security" component doing this.

Finally, it could be an "owner" or "file" permission issue with your hosting account. Judging from the fact that your folder is 777, I assume your hosting company is running PHP on the server as an Apache module. In other words, owner permissions are messed up and in order for Joomla to work, your hosting company is so smart that they decided to give global read/write access to your site's folders... I can't stress how important it is for you to move to another host...

Lastly, on a thread that's currently active, for a product that is 100% free, you should wait a little while before posting in the Joomla! Extensions Directory that K2 sucks extensions.joomla.org/extensions/authoring-a-content/content-construction/8061#rev-157188 - This shows that not only you don't understand open source, you also don't value the time of people who provide free support to you. And therefore you're bashing an entire community for what? Because your hosting company eventually sucks?