XML Problem, not all properties get serialized

[atuvy]

My project includes a class which is serialized to an XML string but for some reason not all of the properties get serialized and I cannot figure out why, pleas help
In the code below callID and global CallID get serilized but "cause" does not

[System.Runtime.Serialization.DataMemberAttribute()]
        public string callID { get; set; }

        [System.Runtime.Serialization.DataMemberAttribute()]
        public string globalCallID { get; set; }

        [System.Runtime.Serialization.DataMemberAttribute()]
        public string cause { get; set; }

this is my serialization code

public string Serializew(object popo,Encoding _Encoding)
        {
            System.IO.StreamReader streamReader = null;
            System.IO.MemoryStream memoryStream = null;
            try
            {
                memoryStream = new System.IO.MemoryStream();
                XmlTextWriter xmlTextWriter = new XmlTextWriter(memoryStream, _Encoding);
                Serializer.Serialize(xmlTextWriter, popo);
                memoryStream.Seek(0, System.IO.SeekOrigin.Begin);
                streamReader = new System.IO.StreamReader(memoryStream);
                return streamReader.ReadToEnd();
            }
            finally
            {
                if ((streamReader != null))
                {
                    streamReader.Dispose();
                }
                if ((memoryStream != null))
                {
                    memoryStream.Dispose();
                }
            }
        }
        private static System.Xml.Serialization.XmlSerializer serializer;
        private static System.Xml.Serialization.XmlSerializer Serializer
        {
            get
            {
                if ((serializer == null))
                {
                    serializer = new System.Xml.Serialization.XmlSerializer(typeof(ImmMessage));
                }
                return serializer;
            }

        }

[atuvy]

Found the problem, it was in my code.