Consider the following beans:

@Startup
@Singleton
public class A
{

@EJB
private B slsb1;

@PostConstruct
public void onConstruct()

}

@Stateless
public class B
{

@EJB
private C slsb2;
}

@Stateless
public class C
{
....
}

Currently, the @Startup @Singleton is instantiated when the ENC of that bean is fully invokable. However, it only waits for a populated ENC of transitive dependent bean(s). This can lead random failures with lookup. Please see the referenced forum thread for the complete details.