Can't upload docx, pptx or xlsx file..

[kieky]

this is my code.. i can upload everything (image, pdf, doc, ppt, xls, text), but i can upload file with Microsoft Office 2007 (docx, pptx, xlsx).. whats wrong with my code? can u help me? Please??

DMSDataAccess db = new DMSDataAccess();
 Dokumen doc = new Dokumen();
 Versi versi = new Versi();
            
 if (FileUpload1.HasFile)
 {
      string strFileName = FileUpload1.FileName.ToString();
      string strExtension = Path.GetExtension(strFileName);
      string strTimeStamp = DateTime.Now.ToString("yyyyMMdd-HHmmss.fff");
      string strName = Path.GetFileNameWithoutExtension(strFileName);
      strFileName = strName + "-" + strTimeStamp + strExtension;
      this.FileUpload1.SaveAs(Server.MapPath(@"~\\Staf\\Uploads\\" +     strFileName.ToString()));
      Label_Upload_Response.Text = "Upload file success!";
      double size_file = FileUpload1.PostedFile.ContentLength;
      string type_file = FileUpload1.PostedFile.ContentType;

      versi.IdDokumen = doc.IdDokumen;
      versi.UrlFile = "Uploads/" + strFileName;
      versi.Size = size_file/1000;
      versi.Type = type_file;
      versi.UserName = HttpContext.Current.User.Identity.Name;
      versi.ModifiedOn = DateTime.Now;
      versi.NoVersi = 1.0;
               
      doc.JudulDokumen = TextBox_Form_Judul.Text;
      doc.Username = HttpContext.Current.User.Identity.Name;
      doc.CreatedOn = DateTime.Now;
      doc.Deskripsi = TextBox_Form_Deskripsi.Text;
      doc.IdCategory = Convert.ToInt32(DropDownList_Form_Category.SelectedValue);
               
      doc.Versis.Add(versi);
      db.DMSDataContext.Dokumens.InsertOnSubmit(doc);
      db.DMSDataContext.Versis.InsertOnSubmit(versi);
      db.DMSDataContext.SubmitChanges();
  }
  else
  {
      Label_Upload_Response.Text = "Please select a file to upload.";
  }