WordPress translation issues

Solution:

Try telling WordPress where exactly to look for the language file. For example, the following assumes the .mo file is located at wp-content/languages/theme-my-login-de_DE.mo

if ( file_exists( WP_LANG_DIR . '/theme-my-login-de_DE.mo' ) )
    load_textdomain( 'theme-my-login', WP_LANG_DIR . '/theme-my-login-de_DE.mo' );