For the first time in many years I am having problems with CKEDitor on one of my live sites.

The strangest thing is that CKEditor is working fine on the identical local clone of this site but on the live site it gives me a blank space where it should show up, be it on a product.php page or a define page or an ezpage. Nothing, silch, nada. Checking the source of the respective page actually shows the html text - but not on the page itself.

Running latest v 4.1.3 of CKEditor, both live and local.

Background:

ZC 1.5.1 just upgraded from 1.3.9h
same plugins installed live and local
PHP 5.4.23 on live site and PHP 5.4.9 on local install

This is what I did so far to find the culprit:

- uninstalled CKEditor completely and reinstalled, both live and local - to no avail
- downloaded entire live site file system to a separate temp folder and did a full file comparison of both - no difference (other than 2 configure.php files ofc)
- checked log files: nada!

Loaded the live site in the latest Firefox and Chromium (Linux Ubuntu 13.10) - same result. Chromium is set to clear all history, cookies etc upon exit so there can't be any leftover stuff which may falsify the output.

At this point in time I am thinking that it may have something to do with the server side PHP extensions (???) and have decided to go and ask for opinions here.

Any ideas please?

Thanks / Frank