Do you have XDebug extension activated ? Indeed, this happens when sub-elements AJAX response is not JSON compliant, like if you have a warning displayed for instance. I'm sure that if you reload the page and you have view caching, the warning will disappear and the sub elements would show normally.
I'm having this error too when I have objects containing images that cannot be processed by EXIF. No big deal, but it produces warnings.
Don't get me wrong... This extension is a must while developing and debugging (not suitable for production though). But this PHP extension can display more warning and notices than if not activated.
A bunch of Data Error issue was fixed in 4.5 / 4.2011, you can either try upgrading or search for issues in the issue tracker. There are plenty of info on the net on how to use FireBug to debug ajax requests, try one of these: http://www.google.no/search?sourceid=chrome&ie=UTF-8&q=using+firebug+to+debug+ajax
In previous version of the documentation and in previous version of eZ Publish, the lib part was not included/needed.
Cheers
I think that I'm not in the case 'data error if the owner of an object has been removed' neither 'issue with quotes in the of objects', but I'm in a virtual host setup but where can I see the RewriteRule, in which file?
the rewrite rules can be found in the .htaccess file in the root directory of eZ Publish or in the Apache configuration file. If you use Debian or Ubuntu on your server, the file you are looking for is probably /etc/apache2/site-enabled/yoursite.
