Localization Works On Localhost But Not In Production Environment

I have this website with english and portuguese support. In localhost everything works fine and the content is translated based on the querystring parameter named "lang". This chunk of code makes the trick in every page:

protected override void InitializeCulture() {
SetCulture(); } private void SetCulture() {
var logger = Util.GetLogger();
string lang = Request.QueryString["lang"];
if (string.IsNullOrEmpty(lang)) { lang = "pt-br"; }
string sessionLang = (string)Session["lang"];
if (sessionLang != lang) { Session["lang"] = lang;
} logger.Log(string.Format("Culture {0} found",lang));
UICulture = lang; Culture = lang;
Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture(lang);
Thread.CurrentThread.CurrentUICulture = new CultureInfo(lang);
logger.Log(string.Format("Cultura {0} set", lang));
base.InitializeCulture(); }

Thanks to the logger I can say for sure that this method is called in both cases (production and localhost). I have two resources files in App_GlobalResources folder:
-WebSitemapGlobal.en-us.resx;
-WebSitemapGlobal.resx;