Problem selecting the value from a JComboBox binded to a list

I have a JComboBox binded to an observable list (result of a jpa query) in a java desktop application. It gets all the values from that 开发者_开发知识库list and displays them correctly, but I'm not able to select any particular value from the dropdown: that is, when I click on the widget the list of options gets displayed correctly, when I click on an item the list closes and the first value is shown independently from the selection of that particular item.

However, no exception is thrown.

This problem occurs if I have more than a model associated to the same entitymanager.

What's wrong with that?

I solved it using two separate entitymanagers for each model I have in the frame.