As I found out in a now round of bug-hunting, this error occurs always, when I want to activate that bean, not only in the described situation. its allways the same stacktrace (the relevant part of course).
I now start to dig into the jboss-source to find out whats happening.
help is still appreciated, as this is a real project-stopper.
what does the implementation of your home method look like (where is the call to getProductId?)
finally I found the bug!!
it was a leftover debug-output in a the product-beans passivate-method which called getProductId() . It seems this was allowed in 2.x and is not allowed in 3.x.