Java - Exception RMI

Hola,
A ver si alguine me puede echar un cable, estoy intentando a traves de RMI que desde un maquina cliente obtenga una los datos de un objeto remoto que esta en otro maquina que hace de servidor. He registrado el objeto con rmiregistry y tambien he añadido al classpath de la maquina cliente el stub generado y tambien he dado permisos en java.policy para poder acceder, pero aun asi me sale esta excepcion:
error unmarshalling return; nested exception is:
java.lang.ClassNotFoundException: NPDBUserInfoRemote (no security manage RMI class loader disabled)
a.rmi.UnmarshalException: error unmarshalling return; nested exception is: java.lang.ClassNotFoundException: NPDBUserInfoRemote (no security manage RMI class loader disabled)
at sun.rmi.registry.RegistryImpl_Stub.lookup(Unknown Source)
at java.rmi.Naming.lookup(Naming.java:84)
at ClienteRMI.main(ClienteRMI.java:32)
sed by: java.lang.ClassNotFoundException: NPDBUserInfoRemote (no security man
r: RMI class loader disabled)
at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:371)
at sun.rmi.server.LoaderHandler.loadClass(LoaderHandler.java:165)
at java.rmi.server.RMIClassLoader$2.loadClass(RMIClassLoader.java:631)
at java.rmi.server.RMIClassLoader.loadClass(RMIClassLoader.java:257)
at sun.rmi.server.MarshalInputStream.resolveClass(MarshalInputStream.jav
00)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:151

at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1435)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1
)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1274)