I got a similar problem when I upgraded to WordPress 3.3.1 from 3.0.x. The cause of it was that I once had a Russian version of WordPress 3.0.x installed. Then I switched back to the English version, but the language setting in wordpress/wp-config.php was Russian (there was the line define('WPLANG', 'ru_RU');) and there were old Russian localization files in wordpress/wp-content/languages that were not upgraded. I could solve the problem either by setting define('WPLANG', ''); or by removing the wordpress/wp-content/languages catalog.
