I get the following ERROR in my GeoServer logs during startup. It immediately follows the WARN level event:
2013-11-06 11:26:02,513 WARN <span class="error">[org.geoserver]</span> - Error connecting to 'Oracle Historical - OSMM'. Disabling.
2013-11-06 11:26:02,529 ERROR <span class="error">[geotools.jdbc]</span> - There's code using JDBC based datastore and not disposing them. This may lead to temporary loss of database connections. Please make sure all data access code calls DataStore.dispose() before freeing all references to it
I wonder if the second (which looks important) is a consequence of the first. (I suspect it can't connect to that database because of our firewall permissions, so the WARN event is our fault).