Unable to acquire conversation lock after 90 seconds

From time to time, I see the following in my logs - and have had users complain about seeing this when drawing reports.

Initially I thought this was due to heavy server/db usage, but this is not the case.

Can someone please explain this to me, or help me resolve? Could this be browser related? Ie, the user clicking around while the report is being generated?

2014-09-04 03:44:13,190 ERROR errorPage_jsp,http-8081-24:559 - stack trace of exception that redirected to errorPage.jsp

org.springframework.webflow.conversation.impl.LockTimeoutException: Unable to acquire conversation lock after 160 seconds

at org.springframework.webflow.conversation.impl.JdkConcurrentConversationLock.lock(JdkConcurrentConversationLock.java:44)

at org.springframework.webflow.conversation.impl.ContainedConversation.lock(ContainedConversation.java:69)

at org.springframework.webflow.execution.repository.support.ConversationBackedFlowExecutionLock.lock(ConversationBackedFlowExecutionLock.java:51)

at org.springframework.webflow.executor.FlowExecutorImpl.resumeExecution(FlowExecutorImpl.java:166)

at sun.reflect.GeneratedMethodAccessor382.invoke(Unknown Source)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)

at java.lang.reflect.Method.invoke(Method.java:597)

at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:318)

at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)

at org.springframework.security.intercept.method.aopalliance.MethodSecurityInterceptor.invoke(MethodSecurityInterceptor.java:66)

at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)

at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)

at $Proxy108.resumeExecution(Unknown Source)

at org.springframework.webflow.mvc.servlet.FlowHandlerAdapter.handle(FlowHandlerAdapter.java:183)

at org.springframework.webflow.mvc.servlet.FlowController.handleRequest(FlowController.java:174)

at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:48)

at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:900)

at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)

at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)

at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:637)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at com.jaspersoft.jasperserver.war.StaticFilesCacheControlFilter.doFilter(StaticFilesCacheControlFilter.java:137)

at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)

at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)

at org.springframework.security.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:399)

at com.jaspersoft.jasperserver.api.security.IPadSupportFilter.doFilter(IPadSupportFilter.java:67)