could you show here the content of CustomWorkHanlders.conf? Once you define your class there it should discover it automatically from there. Make sure that your handler has default (no arg) constructor.
Sure, here's the content of CustomWorkHandlers.conf:
"Log": new org.jbpm.process.instance.impl.demo.SystemOutWorkItemHandler(),
"Email" : new com.sample.NewEmailHandler(),
Also in drools.session.conf:
I'm currently using the default constructor - I hard-coded user information temporarily to make sure there are no errors in passing arguments.
I made a project yesterday using the eclipse editor where I was able to use this handler successfully after a call to ksession.getWorkItemManager().registerWorkItemHandler("Email", NewEmailHandler);