Did you trace SQL statements ?
uncomment tracing in log4j.xml for cmp plugins
i just recreated a project with JBuilder, create a Session Bean an Entity Bean with a primary key composed by thrre fields and changed the log4j properties to tace the sql statements under JBoss.
Well, everything works fine.
I don't know how but it works.
Probably JBuilder did some mistakes to create automatically EJB in my project.
This is a problem of IDE. You never know what IDE did behind. It is better to use XDoclets