Quick uploads not working

Does this also happen on a fresh Drupal installation?

If it's not too difficult ... It is much easier to find the problem if the problem can be reproduced starting from a fresh installation.

Another suggestion: compare file browser settings (old vs new installation) in the FCKeditor profile and save this profile.
Also make sure that you have

require_once '../../../../../filemanager.config.php';

in the right place in the config.php file in the FCKeditor subfolder (more info in README.txt).

I have exactly the same problem with version 6.x-1.3-rc1 and I use IMCE too.
I can upload files with IMCE pop-up, it works very well, it's just with "Quick upload" that it doesn't work.
When I choose my file and click on "send to server" button, the page stays blocked on that screen and the file is not uploaded on the server.
I'll try on a fresh install to see if I have the same bug.

@barako: Humm... does it happen always, or are you able to upload at least small files?
Could you send me a PM with a link where I could see it? Or if you would like to debug it by yourself:
Install Fiddler, launch it and then launch IE (you may use a also different tool that works like a HTTP Proxy).

Search for the following url:
modules/fckeditor/fckeditor/editor/filemanager/connectors/php/upload.php?Type=Image
Click on a Session Inspector tab and take a look at the bottom and press the TextView button (see the screenshot).

You should see there some strange javascript code:

(function(){var d=document.domain;while (true){try{var A=window.parent.document.domain;break;}catch(e) {};d=d.replace(/.*?(?:\.|$)/,'');if (d.length==0) break;try{document.domain=d;}catch (e){break;}}})();window.parent.OnUploadCompleted(0,"/drupal64/sites/default/files/spider.jpg","spider.jpg", "") ;

Let me know what you've got there.

If you get an empty page there, take a look at the errror log or turn on display_errors and error_reporting in this one file (modules/fckeditor/fckeditor/editor/filemanager/connectors/php/upload.php).

Closed because of inactivity. If it is still a problem, please reopen.