The JobScheduler installation shipped with a JDBC driver for oracle which supported Oracle databases up to version 10g. If you want to use version 11 of the oracle database you have to replace the file ojdbc14.jar in the lib folder of your installation with Oracle JDBC 11.1.0.6 driver - not newer (see http://www.oracle.com/technetwork/database/enterprise-edition/jdbc-111060-084321.html).
Thank you for this information to Stephen Windsor, Oracle database administrator at Wesleyan University in Connecticut. It is not confirmed by the developers of JS.