Error in XML Serialization c#.net

I'm working on a WCF service using .net 4.0 framework. I'm trying to serialize the request object using the same type which is already been deserialized by the encorder. but it keeps throwing off for "There was an error generating the XML document". is there anyway that i can get an descriptive error at least?

screenshot of the successfully deserialized request,

errornous code that supposed to serialize the object,

    XmlSerializer serializer = new XmlSerializer(typeof(ResourceParticipantDataRequest));
    StringWriter writer = new StringWriter();
    serializer.Serialize(writer, resourceParticipantData);

the Error,

    ----Inner Exception:
----Type: System.ServiceModel.FaultException`1[[System.ServiceModel.ExceptionDetail, System.ServiceModel, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]
----Message: There was an error generating the XML document.
----Source: mscorlib
----StackTrace: 

Please help! i'm running out of options.