Editor - Article (editor-xtd) Plug In Problem

[richard007]

I have a problem with the article plugin for Joomla 2.5x i.e the button for inserting article links at the bottom of a Joomla editor window.

In some of my Joomla installations it doesn't work. By which I mean the plugin is enabled and is visible in the editor window (JCE/Rokpad/JCK etc) and I can click on it to bring up the list of articles. Problem is nothing happens when I select an article. The window sits there , the cursor even turns into a hand but nothing happens.

1) Plugin is enabled
2) It happens whichever editor I am using
3) Same result in FF and Opera on Linux , FF on Win8
4) Disabling and re-enabling the plugin doesn't fix it.
5) I generally use the same extensions for all sites
6) Not found anything (for once) on Google.

So it's looking like a specific install problem of some sort.

Anyone got any diagnostic suggestions ? I've been pulling my hair out over this since September. My suspicions (without any actual foundation as I'm at the guessing stage) are either RS Firewall (although all sites have it) or some .htaccess weirdness.