This connection has been closed

I am using a cdo server (org.eclipse.emf.cdo) which uses hibernate which
uses the postgresql jdbc driver. (9.0.0.801)
Between two transactions the tcp connection between the cdo server and
postgresql went down (my laptop hibernated).
I got an exception with this cause:

Caused by: org.postgresql.util.PSQLException: This connection has been
closed.
     at
org.postgresql.jdbc2.AbstractJdbc2Connection.checkClosed(AbstractJdbc2Connection.java:714)
     at
org.postgresql.jdbc2.AbstractJdbc2Connection.getAutoCommit(AbstractJdbc2Connection.java:680)
     at
org.hibernate.connection.DriverManagerConnectionProvider.getConnection(DriverManagerConnectionProvider.java:127)
     at
org.hibernate.jdbc.ConnectionManager.openConnection(ConnectionManager.java:446)

This might be related to this issue:
https://forum.hibernate.org/viewtopic.php?f=1&t=957369

Do we have a hibernate, a postgresql or a CDO issue here?