Erro ao fazer update "Vraptor + Hibernate + Spring"

Ao fazer um update em uma logica OneToMany da o seguinte erro:

Abr 03, 2012 2:33:33 PM org.apache.catalina.core.StandardWrapperValve invoke Grave: Servlet.service() for servlet [default] in context with path [/futura] threw exception br.com.caelum.vraptor.InterceptionException: exception raised, check root cause for details: org.springframework.dao.InvalidDataAccessApiUsageException: object references an unsaved transient instance - save the transient instance before merging: ws.futuranet.modelo.Usuario; nested exception is org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before merging: ws.futuranet.modelo.Usuario at br.com.caelum.vraptor.interceptor.ExecuteMethodInterceptor.intercept(ExecuteMethodInterceptor.java:96) at br.com.caelum.vraptor.core.ToInstantiateInterceptorHandler.execute(ToInstantiateInterceptorHandler.java:54) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.core.LazyInterceptorHandler.execute(LazyInterceptorHandler.java:61) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.interceptor.ParametersInstantiatorInterceptor.intercept(ParametersInstantiatorInterceptor.java:87) at br.com.caelum.vraptor.core.LazyInterceptorHandler.execute(LazyInterceptorHandler.java:59) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.util.hibernate.HibernateTransactionInterceptor.intercept(HibernateTransactionInterceptor.java:48) at br.com.caelum.vraptor.core.ToInstantiateInterceptorHandler.execute(ToInstantiateInterceptorHandler.java:54) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.core.LazyInterceptorHandler.execute(LazyInterceptorHandler.java:61) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.interceptor.ExceptionHandlerInterceptor.intercept(ExceptionHandlerInterceptor.java:71) at br.com.caelum.vraptor.core.ToInstantiateInterceptorHandler.execute(ToInstantiateInterceptorHandler.java:54) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.interceptor.InstantiateInterceptor.intercept(InstantiateInterceptor.java:48) at br.com.caelum.vraptor.core.ToInstantiateInterceptorHandler.execute(ToInstantiateInterceptorHandler.java:54) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.interceptor.FlashInterceptor.intercept(FlashInterceptor.java:83) at br.com.caelum.vraptor.core.ToInstantiateInterceptorHandler.execute(ToInstantiateInterceptorHandler.java:54) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.interceptor.ResourceLookupInterceptor.intercept(ResourceLookupInterceptor.java:69) at br.com.caelum.vraptor.core.ToInstantiateInterceptorHandler.execute(ToInstantiateInterceptorHandler.java:54) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.core.ToInstantiateInterceptorHandler.execute(ToInstantiateInterceptorHandler.java:56) at br.com.caelum.vraptor.core.DefaultInterceptorStack.next(DefaultInterceptorStack.java:54) at br.com.caelum.vraptor.core.EnhancedRequestExecution.execute(EnhancedRequestExecution.java:44) at br.com.caelum.vraptor.VRaptor$1.insideRequest(VRaptor.java:92) at br.com.caelum.vraptor.ioc.spring.SpringProvider.provideForRequest(SpringProvider.java:58) at br.com.caelum.vraptor.VRaptor.doFilter(VRaptor.java:89) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100) at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188) at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at java.lang.Thread.run(Unknown Source)

Segue código para ajudar;

Grupo:

@OneToMany(cascade={CascadeType.MERGE}, targetEntity=Usuario.class, fetch=FetchType.EAGER) @JoinColumn(name="grupoComoEntrevistador_id") private Collection<Usuario> entrevistadores;

Usuário:

@ManyToOne private Grupo grupoComoEntrevistador;

GrupoController:

// Alterar Grupos public void alterar(Grupo grupoEntrevistador) throws CadastroException { grupoDAO.alterar(grupoEntrevistador); result.include("grupoEntrevistador", grupoEntrevistador); result.use(Results.logic()).redirectTo(GruposController.class).lista(); }

GrupoDAO:

@Transactional public Grupo alterar(Grupo grupo) throws CadastroException { Update(grupo); return grupo; }