I was wondering if you managed to find a way of making the helper classes accessible to the EJBs without including them in the EJB jar file.
I have the same problem with my application. Unfortunately, the JBoss Tutorial does not cover helper classes and their deployment. So, I'm left guessing as to how I sould go about deploying my _other_ classes: those that are not servlets or EJBs.
Have you tried add a Class-Path: entry in your manifest.mf file of your ejb.jar? Is this manner, this jar will be in the ejb-jar's classpath.