Serialization / Deserialization problem in C#

/// <summary>
/// Serializes an object.
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="serializableObject"></param>
/// <param name="fileName"></param>
public void SerializeObject<T>(T serializableObject, string fileName)
{
    if (serializableObject == null) { return; }
    try
    {
        XmlDocument xmlDocument = new XmlDocument();
        XmlSerializer serializer = new XmlSerializer(serializableObject.GetType());
        using (MemoryStream stream = new MemoryStream())
        {
            serializer.Serialize(stream, serializableObject);
            stream.Position = 0;
            xmlDocument.Load(stream);
            xmlDocument.Save(fileName);
            stream.Close();
        }
    }
    catch (Exception ex)
    {
        //Log exception here
    }
}


/// <summary>
/// Deserializes an xml file into an object list
/// </summary>
/// <typeparam name="T"></typeparam>
/// <param name="fileName"></param>
/// <returns></returns>
public T DeSerializeObject<T>(string fileName)
{
    if (string.IsNullOrEmpty(fileName)) { return default(T); }
    T objectOut = default(T);
    try
    {
        string attributeXml = string.Empty;
        XmlDocument xmlDocument = new XmlDocument();
        xmlDocument.Load(fileName);
        string xmlString = xmlDocument.OuterXml;

        using (StringReader read = new StringReader(xmlString))
        {
            Type outType = typeof(T);
            XmlSerializer serializer = new XmlSerializer(outType);
            using (XmlReader reader = new XmlTextReader(read))
            {
                objectOut = (T)serializer.Deserialize(reader);
                reader.Close();
            }
            read.Close();
        }
    }
    catch (Exception ex)
    {
        //Log exception here
    }
    return objectOut;
}