This does look like a class-path issue. I would look closely to see if you have multiple copies of any class/interface in the classpath. If so, you'll need to remove them and set module depenencies correctly.
Independent Consultant — Author, EJB 3 in Action — Expert Group Member, Java EE 6 and EJB 3.1
I am using Netbeans6.1RC2 to create a independant EJB module with the stateless bean code as shown in the above message. My EJB module only consists of a sample Bean and a the Bean Interface.
Then I deploy the ejb module in JBoss4.2.2GA.
Now I create a seperate web application project to which I have added this ejb jar file to my project lib.
I am importing the package into my JSP and just doing a lookup for the same.