Calling WCF service w/ ProtoBehavior and multiple parameters

Question

This one has me puzzled and am hoping it's a silly oversight on my part. When I call the following web service, if a null parameter is encountered then all following parameters are null (or zero for the numerics).

[OperationContract, ProtoBehavior]
[ServiceKnownType(typeof(ServiceFault))]
[FaultContract(typeof(ServiceFault))]
PersonProfileMessagePart Create(ObjectId person, ObjectId industry, int yearsInIndustry, ObjectId occupation, string occupationFreeText,
                                int yearsInOccupation, string maritalStatus, string educationLevel, 
                                List<ChildMessagePart> children, FinancialProfileMessagePart financialProfile,
                                List<ObjectId> traits);

For example, if person and yearsInIndustry are present but not industry, all parameters including yearsInIndustry default to null/zero. Is there an additional attribute I need to apply?

{edit} My bad. Marc, it is WCF with a custom binding.

<customBinding>
 <binding name="ServiceFedBinding">
  <security authenticationMode="SecureConversation">
   <secureConversationBootstrap authenticationMode="IssuedToken">
    <issuedTokenParameters tokenType="http://docs.oasis-open.org/wss/oasis-wss-saml-token-profile-1.1#SAMLV1.1"&gt;
     <issuer address="http://links-dev:91/security/authentication/securetokenservice.svc/" binding="wsHttpBinding">
      <identity>
       <dns value="LINKS"/>
      </identity>
     </issuer>
     <issuerMetadata address="http://links-dev:91/security/authentication/securetokenservice.svc/mex"/&gt;
    </issuedTokenParameters>
   </secureConversationBootstrap>
  </security>

Thanks in advance. Mike