It was not possible to complete the request due to file

Thanks for opening,

I get the following error:

It was not possible to complete the request due to file system permission restrictions.

domain in this case is domainname.nl

What I've tried:
I've succesfully integrated CKeditor. I installed ckfinder in the root map (same map as ckeditor is in), I set the authentication to return true; for testing purposes. I didn't change the baseURL and baseDIR and then set CHMOD on userfiles to 777. I went to 'http://www.domainname.nl/ckfinder/_samples/js/ckeditor.html'. The editor works but as soon as I want to upload I get the error as said above. After that I tried integrating both ways (with CKFinder.SetupCKEditor() and by setting the options. Not changing config.php and tried again. Again the same error. I then changed .htaccess in /userfiles/ to turn safemode off. I still got the same error.
Up next I moved the ckfinder folder to the ckeditor folder and changed the link in the baseDIR and baseURL and the links in the actual phpfile where ckfinder is integrated. I still get to use ckfinder but the upload doesn't work (and I don't get to see any folders).
I then tried several baseDirs and baseURLs as shown below. (I'd like to note one thing that the baseURL seems right because when I click upload, click OK at the error and get taken back to the 'information' tab I see the right URL: 'http://www.domainname.nl/ckeditor/ckfinder/userfiles/images/filename.png)

These are the combinations of baseDIR and baseURL I've used:
$baseUrl = '/userfiles/';
$baseDir = resolveUrl($baseUrl);

$baseUrl = '/ckfinder/userfiles/';
$baseDir = resolveUrl($baseUrl);

$baseUrl = '/ckeditor/ckfinder/userfiles/';
$baseDir = resolveUrl($baseUrl);

$baseUrl = 'http://www.domainname.nl/ckeditor/ckfinder/userfiles/';
$baseDir = resolveUrl($baseUrl);

all of the above but with the following $baseDirs:
/domains/domainname.nl/public_html/ckeditor/ckfinder
/ckeditor/ckfinder

I currently have the following values:
$baseUrl = 'http://www.domainname.nl/ckeditor/ckfinder/userfiles/';
$baseDir = '/userfiles/';

As you can see I became quite desperate. I've had a couple more combinations and so far it's been taking me over 16 hours. I'd like to note that one time I didn't get the error but it said it couldn't find the connector file (which I checked the path of and seemed to be right). I later restored back to the exact same settings and got the error again.

Thanks in advance.