Value does not fall in the expected range

I have SharePoint blog in English and Arabic language versions. By C# code i inserted successfully a new item to Blog post. But while I try to insert a new item in the Arabic version then its giving error: Value does not fall within the expected range.

Is there any setting I have to change in here. Please see my code here.

string DURL = "http://mysite/Arabic/Blog1/Lists/Posts/";
            using (SPSite site = new SPSite(DURL))
             
            {
              using (SPWeb web = site.OpenWeb())
              {

               
                web.AllowUnsafeUpdates = true;
                SPList list = web.Lists["Posts"];

                SPUser user = web.EnsureUser(HttpContext.Current.User.Identity.Name);
                SPListItem Item1 = list.Items.Add();
                Item1["Title"] = TxtTitle.Text;
                Item1["Body"] = TxtBody.Text;
                Item1.Fields["Created By"].ReadOnlyField = false;

                Item1["Published"] = System.DateTime.Now;
                string userValue = user.ID + ";#" + user.Name;
                Item1["Created By"] = userValue;
                Item1.Update();
                Item1.Fields["Created By"].ReadOnlyField = true;
              }
            }