thank you Bukkit...

gistfile1.txt

    private static boolean languageWorkaroundInitialized;
    private static Field localeStringField;
    private static Field handleField;
    private static Field localeField;
    
    static
    {
        try
        {
            localeStringField = Class.forName("net.minecraft.server.LocaleLanguage").getDeclaredField("d");
            localeStringField.setAccessible(true);
            
            handleField = Class.forName("org.bukkit.craftbukkit.entity.CraftPlayer").getDeclaredField("entity");
            handleField.setAccessible(true);
            
            localeField = Class.forName("net.minecraft.server.EntityPlayer").getDeclaredField("locale");
            localeField.setAccessible(true);
            
            languageWorkaroundInitialized = true;
        }
        catch (Exception e)
        {
            languageWorkaroundInitialized = false;
        }
    }
    
    public String getLanguage()
    {
        if (languageWorkaroundInitialized)
        {
            try
            {
                return (String)localeStringField.get(localeField.get(handleField.get(this)));
            }
            catch (Exception e)
            {}
        }
        return CubeEngine.getCore().getConfiguration().defaultLanguage;   
    }