Message board error

[eilab eilab, modificado hace 15 años.]

We are using Liferay 5.1.2 bundled with tomcat 5.5. We encountered some problems with message board. Sometimes we are not able to post message and the server displays a page error saying "Message Board temporarily unavailable".
In log file we can see the stacktrace starts from exception like this (the full stacktrace is very long to post here):

11:00:08,703 ERROR [jsp:52] com.liferay.portal.kernel.dao.orm.ORMException: could not load an entity: [com.liferay.counter.model.Counter#com.liferay.portlet.social.model.SocialActivity]
at com.liferay.portal.dao.orm.hibernate.ExceptionTranslator.translate(ExceptionTranslator.java:41)
at com.liferay.portal.dao.orm.hibernate.SessionImpl.get(SessionImpl.java:111)
at com.liferay.counter.service.persistence.CounterPersistence.createCounterRegister(CounterPersistence.java:275)
at com.liferay.counter.service.persistence.CounterPersistence.createCounterRegister(CounterPersistence.java:261)
at com.liferay.counter.service.persistence.CounterPersistence.getCounterRegister(CounterPersistence.java:252)
at com.liferay.counter.service.persistence.CounterPersistence.increment(CounterPersistence.java:116)
at com.liferay.counter.service.persistence.CounterPersistence.increment(CounterPersistence.java:106)
at com.liferay.counter.service.persistence.CounterUtil.increment(CounterUtil.java:46)
at com.liferay.counter.service.impl.CounterLocalServiceImpl.increment(CounterLocalServiceImpl.java:48)
at com.liferay.portlet.social.service.impl.SocialActivityLocalServiceImpl.addActivity(SocialActivityLocalServiceImpl.java:65)
at com.liferay.portlet.social.service.impl.SocialActivityLocalServiceImpl.addActivity(SocialActivityLocalServiceImpl.java:52)
at com.liferay.portlet.messageboards.service.impl.MBMessageLocalServiceImpl.addMessage(MBMessageLocalServiceImpl.java:537)
at com.liferay.portlet.messageboards.service.impl.MBMessageLocalServiceImpl.addMessage(MBMessageLocalServiceImpl.java:262)
at com.liferay.portlet.messageboards.service.impl.MBMessageLocalServiceImpl.addMessage(MBMessageLocalServiceImpl.java:244)
at com.liferay.portlet.messageboards.service.impl.MBMessageServiceImpl.addMessage(MBMessageServiceImpl.java:204)
at com.liferay.portlet.messageboards.service.MBMessageServiceUtil.addMessage(MBMessageServiceUtil.java:109)
at com.liferay.portlet.messageboards.action.EditMessageAction.updateMessage(EditMessageAction.java:241)
at com.liferay.portlet.messageboards.action.EditMessageAction.processAction(EditMessageAction.java:86)
at com.liferay.portal.struts.PortletRequestProcessor.process(PortletRequestProcessor.java:180)
at com.liferay.portlet.StrutsPortlet.processAction(StrutsPortlet.java:197)


The only way to make liferay work again is to restart tomcat
Could anyone help us please?

Thanks