Oops, make that:
clazz = (clazz == null) ? getParent().findClass(name) : clazz;
Forgot that there isn't a default findClass impl on ClassLoader.class.
Forget it. Original problem was an operator error. One char wrong in the action class name in the process definition. Time to bump up the font size by 1. :)
Also, found that my suggested tweak wasn't viable, the parent class loader's findClass method isn't public, so you would have to use getParent().loadClass(name) - which of course didn't make any difference since my class name was wrong in the first place.
Actually, when you implement a custom class loader you don't have to call the parent class loader yourself. Consider the JDK 1.4 API docs for ClassLoader.findClass():
This method [...] will be invoked by the loadClass method after checking the parent class loader for the requested class