Hi, I have dared to extend MeasurementReport by adding LinkedHashSets of ExecutionTimeDataBeans and ResponseTimeDataBeans (my beans for some type of call time data). Both beans implement Externalizable to read/write themselves. All is fine, until the server tries to read from the input stream the MeasurementReport sent by an agent. It then fails with an java.io.OptionalDataException trying to read in the LinkedHashSet of ResponseTimeDataBean. At the point at which this happens the LInkedHashSet isEmpty, so all MeasurementReport.readExternal would need to do is read in an empty Set<ResponseTimeDataBean>. Has anyone come across such an issue before? Is there something obvious I may be missing (such as don't try to serialize entity beans, or I don't know what). I am asking as I'm hoping that someone has come across this or a similar situation when working on serialization between agent and server and because I am out of ideas. Thanks, -- Bruno