Since ez4.4 (I guess), my ezoe doesn't show...

In fact firebug tells me the file /extension/ezoe/design/standard/javascript/langs/-eng-GB.js is lacking

And indeed, this file really doesn't exist, all the file I can see is: /extension/ezoe/design/standard/javascript/langs/en.js

It seems to come from the file:
extension/ezoe/design/standard/templates/content/datatype/edit/ezxmltext_ezoe.tpl.

We can see at the beginning, the definition of $language (around line 24):

$language         = '-'|concat( $ez_locale )

hence the $langage = -eng-GB in my case, and later on (around line 71), there's some js code in charge of loading ezoe:

 var eZOeAttributeSettings, eZOeGlobalSettings = {ldelim}
        mode : "none",
        theme : "ez",
        width : '100%',
        language : '{$language}',
        skin : '{$skin}',

so eZOeGlobalSettings.language is set to '-eng-GB'

and later on (around line 140), we can see:

(function(){
        var uri = document.location.protocol + '//' + document.location.host + eZOeGlobalSettings.ez_tinymce_url, tps = eZOeGlobalSettings.plugins.split(','), pm = tinymce.PluginManager, tp;
        tinymce.ScriptLoader.markDone( uri.replace( 'tiny_mce', 'langs/' + eZOeGlobalSettings.language ) );
        for (var i = 0, l = tps.length; i < l; i++)
        {
            tp = tps[i].slice(1);
            pm.urls[ tp ] = uri.replace( 'tiny_mce.js', 'plugins/' + tp );
        }
    }())

=> ezoe wants to load 'langs/' + eZOeGlobalSettings.language, that is langs/-eng-GB.js, hence my firebug error...

In order to correct this problem, I've just performed a symlink from -eng-GB.js to en.js, and it perfectly works
Of course, this is just a workaround...

I guess, best solution would be to have $language = $ez_locale, and in extension/ezoe/design/standard/javascript/langs, a bunch of files for each locale supported by eZ, eng-GB.js, fre-FR.js, etc...