DownloadUpdate() doesn't work


I am using the next code:

AutoUpdater.CurrentCulture = System.Globalization.CultureInfo.CreateSpecificCulture("es-MX");
AutoUpdater.LetUserSelectRemindLater = false;
AutoUpdater.RemindLaterTimeSpan = RemindLaterFormat.Days;
AutoUpdater.RemindLaterAt = 1;
AutoUpdater.OpenDownloadPage = false;
//AutoUpdater.Start(Utils.Utils.IP_ADDRESS + "updater/" + msg);
AutoUpdater.AppCastURL = Utils.Utils.IP_ADDRESS + "updater/" + msg;

I need to download the update without asking the user if he wants to, so i am using the DownloadUpdate() method, the problem is that it never download anything and throws me this exception: A first chance exception of type 'System.ArgumentNullException' occurred in System.dll
How can i achieve this?

On the other hand, i cant change the CurrentCulture of the AutoUpdater, even if i set it as the example tutorial it doesnt work, how can i change it to spanish?