I get the following error when trying to set a variable for a taskInstance.

[LazyInitializationException] could not initialize proxy - the owning Session was closed
org.hibernate.LazyInitializationException: could not initialize proxy - the owning Session was closed
 at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:56)
 at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:98)
 at org.hibernate.proxy.CGLIBLazyInitializer.intercept(CGLIBLazyInitializer.java:133)
 at org.jbpm.taskmgmt.exe.TaskInstance$$EnhancerByCGLIB$$89d6f052.setVariable(<generated>)
 at org.jbpm.webapp.bean.TaskBean.save(TaskBean.java:179)
 at kernel.bpcs.RequisicionBPCS.guardarTarea(RequisicionBPCS.java:350)
 at kernel.bpcs.RequisicionBPCS.guardar(RequisicionBPCS.java:517)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
 at java.lang.reflect.Method.invoke(Unknown Source)
 at org.apache.myfaces.el.MethodBindingImpl.invoke(MethodBindingImpl.java:129)
 at org.apache.myfaces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:63)
 at javax.faces.component.UICommand.broadcast(UICommand.java:106)
 at javax.faces.component.UIViewRoot._broadcastForPhase(UIViewRoot.java:90)
 at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:164)
 at org.apache.myfaces.lifecycle.LifecycleImpl.invokeApplication(LifecycleImpl.java:271)
 at org.apache.myfaces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:86)
 at javax.faces.webapp.FacesServlet.service(FacesServlet.java:94)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:147)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.jbpm.web.AuthenticationFilter.doFilter(AuthenticationFilter.java:56)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.jbpm.web.JbpmContextFilter.doFilter(JbpmContextFilter.java:85)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:81)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
 at org.jboss.web.tomcat.security.CustomPrincipalValve.invoke(CustomPrincipalValve.java:39)
 at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:159)
 at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:59)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856)
 at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744)
 at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
 at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
 at java.lang.Thread.run(Unknown Source)

public void save(Hashtable taskVariables, String transition)
 {

 TaskInstance taskInstance = taskMgmtSession.loadTaskInstance(taskInstanceId);

 if(taskVariables != null && taskVariables.size() > 0)
 {
 Iterator i = taskVariables.keySet().iterator();
 while(i.hasNext()){
 String key = (String)i.next();
 Object value = taskVariables.get(key);
 taskInstance.setVariable(key, value);
 }
 }
 taskInstance.end(transition);

 jbpmContext.save(taskInstance);


 }