WP_editor - URL popup doesn't work

I was asked to fix a problem with adding an url, while adding a new content via built-in editor. Upon clicking the "chain" icon, the little window pops up, true, but then the whole site goes dark, as if jquery modal window has been opened, and the url-popup is hidden behind it.

Only one thing is left then, which is clicking a screen to close the popup/modal.

I guess the problem lies with a conflict between wp_editor and one of the plugins (and there are PLENTY of them!) but I cannot locate it.

This piece of code initiates the editor:

<div class="tinymce-holder">
<?php wp_editor( stripcslashes($_POST['article_content']) ,'article_content',
        array(
                'media_buttons'=> false,
                'teeny'=> false,
                'wpautop'=> false,
                'quicktags'=> false,
                'textarea_rows' => 30,
                'tinymce' => true        
        )        
    );?>
</div>

Has anyone seen anything like it and could help me out here? Any input would be appreciated.

Thanks,

Cheers,

Greg