I'm getting the error listed below from a DD4T-enabled site I'm trying to work. I've verifed my DB connection info & it looks correct. Is this a license issue? Is the "Cannot open connection" error really causing this?

    2013-09-10 14:46:06,534 ERROR SessionsCleanerMonitor - Could not perform sessions clean-up. Will retry in 120000 milliseconds.
javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: Cannot open connection
    at org.hibernate.ejb.AbstractEntityManagerImpl.throwPersistenceException(AbstractEntityManagerImpl.java:614) ~[hibernate-entitymanager.jar:3.4.0.GA]
    at org.hibernate.ejb.QueryImpl.getResultList(QueryImpl.java:76) ~[hibernate-entitymanager.jar:3.4.0.GA]
    at com.tridion.storage.persistence.JPABaseDAO.executeQueryListResult(JPABaseDAO.java:266) ~[cd_datalayer.jar:na]
    at com.tridion.storage.persistence.JPABaseDAO.executeQueryListResult(JPABaseDAO.java:234) ~[cd_datalayer.jar:na]
    at com.tridion.storage.persistence.JPABaseDAO.executeQueryListResult(JPABaseDAO.java:217) ~[cd_datalayer.jar:na]
    at com.tridion.storage.session.persistence.JPAPreviewSessionDAO.getExpiredSessions(JPAPreviewSessionDAO.java:84) ~[cd_session.jar:na]
    at com.tridion.storage.session.SessionServiceImpl.getExpiredSessions(SessionServiceImpl.java:75) ~[cd_session.jar:na]
    at com.tridion.storage.session.SessionManagerImpl.performCleanup(SessionManagerImpl.java:227) ~[cd_session.jar:na]
    at com.tridion.storage.persistence.session.SessionsCleanerMonitor.run(SessionsCleanerMonitor.java:54) ~[cd_session.jar:na]