A possible solution for your issue :
// Change your Message's ConfigurationElements property with this
[XmlArray("release")]
[XmlArrayItem("rlse")]
public List<ConfigurationElement> ConfigurationElements { get; set; }
You'll be able to get rid of your mid-class ConfigurationElements and help the Xml parser.
You should probably pass the Encoding as a parameter to the Serialization / Deserialization, could help.