I found error in cd_preview
log file of staging website which is
ERROR SessionWrapperFactory - Exception while cleaning-up session data: Error while committing the transaction, Error while committing the transaction 2013-12-12 16:05:03,727 TRACE SessionsCleanerMonitor - Could not perform sessions clean-up. Will retry in 60000 milliseconds. com.tridion.storage.persistence.session.SessionHandlingException: Could not clean session storage after session expired: Exception while cleaning-up session data: Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Exception while cleaning-up session data: Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Exception while cleaning-up session data: Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction, Error while committing the transaction at com.tridion.storage.session.SessionManagerImpl.expireSession(SessionManagerImpl.java:443) ~[cd_session.jar:na] at com.tridion.storage.session.SessionManagerImpl.performCleanup(SessionManagerImpl.java:230) ~[cd_session.jar:na] at com.tridion.storage.persistence.session.SessionsCleanerMonitor.run(SessionsCleanerMonitor.java:52) ~[cd_session.jar:na] at java.lang.Thread.run(Unknown Source) [na:1.7.0_21]
UPDATE : Getting different error now after updating to 2013 sp1
ERROR SessionWrapperFactory - Exception while cleaning-up session data
com.tridion.broker.StorageException: Rollback took place, didn't remove
at com.tridion.storage.persistence.JPABaseDAO.remove(JPABaseDAO.java:155) ~[cd_datalayer.jar:na]
at com.tridion.storage.persistence.JPAItemDAO.remove(JPAItemDAO.java:246) ~[cd_datalayer.jar:na]
at com.tridion.storage.persistence.session.SessionWrapperFactory.deleteItemMeta(SessionWrapperFactory.java:184) ~[cd_session.jar:na]
at com.tridion.storage.persistence.session.SessionWrapperFactory.cleanupSessionData(SessionWrapperFactory.java:161) ~[cd_session.jar:na]
at com.tridion.storage.session.SessionManagerImpl.expireSession(SessionManagerImpl.java:414) [cd_session.jar:na]
at com.tridion.storage.session.SessionManagerImpl.performCleanup(SessionManagerImpl.java:230) [cd_session.jar:na]
at com.tridion.storage.persistence.session.SessionsCleanerMonitor.run(SessionsCleanerMonitor.java:52) [cd_session.jar:na]
at java.lang.Thread.run(Unknown Source) [na:1.7.0_21]
Caused by: java.lang.IllegalArgumentException: attempt to create delete event with null entity
at org.hibernate.event.spi.DeleteEvent.<init>(DeleteEvent.java:45) ~[hibernate-core.jar:4.0.1.Final]
at org.hibernate.internal.SessionImpl.delete(SessionImpl.java:801) ~[hibernate-core.jar:4.0.1.Final]
at org.hibernate.ejb.AbstractEntityManagerImpl.remove(AbstractEntityManagerImpl.java:883) ~[hibernate-entitymanager.jar:4.0.1.Final]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.7.0_21]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[na:1.7.0_21]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[na:1.7.0_21]
at java.lang.reflect.Method.invoke(Unknown Source) ~[na:1.7.0_21]
at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:365) ~[spring-orm.jar:3.1.0.RELEASE]
at com.sun.proxy.$Proxy30.remove(Unknown Source) ~[na:na]
at com.tridion.storage.persistence.JPABaseDAO.remove(JPABaseDAO.java:145) ~[cd_datalayer.jar:na]
... 7 common frames omitted