Hi all, as the same entities as the ones used on the server are also sent to the client (e.g. org.ovirt.engine.core.common.businessentities.VM), this entities will than be serialized/deserialized using the GWT serialization. It means, this entities should follow the restrictions given by the GWT serialization: http://code.google.com/webtoolkit/doc/latest/DevGuideServerCommunication.... "Fields that are declared final are also not exchanged during RPCs, so they should generally be marked transient as well." It means, that no fields which will be sent to client should be marked with the final keyword. Thanks, Tomas