7u55 changed the implementation of
org/omg/CORBA/ORB.init() such that it now
attempts to load the ORB singleton class using the system class loader.
The previous behaviour was to use the thread context class loader.
This causes problems when the ORBSingleton class is not on the system class loader's
classpath - e.g. in the case of a third party ORB shipped with an applet.
In this scenario the init() API fails to load the singleton ORB, as specified in the system property org.omg.CORBA.ORBSingletonClass,
and you get an Exception:
org.omg.CORBA.INITIALIZE: Could not initialize can't instantiate default ORB
Caused by: java.lang.ClassNotFoundException