The function load_plugin_textdomain() is called before the locale is correctly set (especially if you use a multi-lingual plugin).
The function load_plugin_textdomain() should be called in the action 'plugins_loaded' as in this code:
function admin_bar_disabler_init() {
load_plugin_textdomain('admin-bar-disabler', false, basename(dirname(__FILE__)) . 'languages/');
}