I still can't explain the mysterious breakage that started when using another entityManager, but it went away when I switched from a javabean to a SFSB, something I was going to do eventually anyway. I was still seeing dirty data, but I found it was the database I was using -- it looks like HSQLDB only supports Read Uncommitted isolation (it really shouldn't be called isolation at all). Obviously I was going to switch out DB's too .. I guess the moral of the story is to develop for the platform you expect to use sooner rather than later. If I ever puzzle this out, I'll try submitting a wiki as an example application -- it's the simplest real-world app I can think of where you'd want uniqueness and concurrency control with "retry" options in the UI. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3982486#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...