I needed Swedish translation, so I installed TinyMCE Advanced and copied the translation file sv_dlg.js and langs.php from plugins/tinymce-advanced/mce/table/langs to plugins/mce-table-buttons/mce-table/langs
Perfect! it works!
Maybe helpful for others.
EDIT: O, I forgot to tell you I previously had installed translation to TinyMCE, otherwise there will be no swedish language file there to copy…