WordPress Admin Menu Not Visible After Upgrading qTranslate Plugin for Russian

When updating some outdated WordPress site to newest versions of core and plugins the side menu bar in wp administration had mystically disappeared. After examining the cause, by disabling plugins one by one (accessed them from /wp-admin/plugins.php) I found that the cause is qTranslate multi-language plugin.

Examining HTML and CSS with Firebug I found that the menu is not disappeared, it’s just hidden because of some CSS issue. The bug came from Russian CSS file in /wp-content/languages/ru_RU.css, which wasn’t updated from 2010, and therefore caused problems with newest WP Admin interface. Just cleaning the file contents was fixing the menu. Then I cleaned also ru_RU-ie.css to be sure 🙂 The Admin menu shows fine now and crazy issue got resolved.