Error unmarshaling return; nested exception is:

[Aravind_RP]

hi
When i try to access my service using rmi it throws the following exception..

Error unmarshaling return; nested exception is:
        java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: org.ofbiz.service.ModelNotification
java.rmi.UnmarshalException: Error unmarshaling return; nested exception is:
        java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: org.ofbiz.service.ModelNotification
        at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:217)
        at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:126)
        at org.ofbiz.service.rmi.RemoteDispatcherImpl_Stub.runSync(Unknown Source)
        at Hello3Client.main(Hello3Client.java:59)
Caused by: java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: org.ofbiz.service.ModelNotification
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1303)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:339)
        at javolution.util.FastList.readObject(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:585)
        at java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:919)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1813)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1713)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1912)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1836)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1713)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
        at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1912)
        at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1836)
        at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1713)
        at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
        at java.io.ObjectInputStream.readObject(ObjectInputStream.java:339)
        at sun.rmi.transport.StreamRemoteCall.executeCall(StreamRemoteCall.java:215)
        ... 3 more
Caused by: java.io.NotSerializableException: org.ofbiz.service.ModelNotification
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1075)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:291)
        at javolution.util.FastList.writeObject(Unknown Source)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:585)
        at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:890)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1333)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1284)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1073)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1369)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1341)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1284)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1073)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1369)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1341)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1284)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1073)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:291)
        at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:332)
        at sun.rmi.transport.Transport$1.run(Transport.java:153)
        at java.security.AccessController.doPrivileged(Native Method)
        at sun.rmi.transport.Transport.serviceCall(Transport.java:149)
        at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:460)
        at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:701)
        at java.lang.Thread.run(Thread.java:595)

my service definitions and service.xml as follows

<service name="retriveCateogaryId" engine="java" auth="false" export="true"
        location="org.ofbiz.hello3.Hello3Services" invoke="retriveCateogaryId">
        <description>Retrives all Cateogary Id</description>
        <attribute name="productStoreId" mode="IN" type="String" optional="true"/>
         <attribute name="userLoginId" mode="IN" type="String" optional="true"/>
        <attribute name="cateogaryId" mode="OUT" type="String" optional="false"/>
        </service>

and am invoking through a client.

resultQuery = rd.runSync("retriveCateogaryId",
                    UtilMisc.toMap("productStoreId","9000"));

please if any one can suggest a solution