So, nobody has any ideas? Or is the problem trivial, and it is just me that I cannot notice the cause? In the latter case I would be thankful for any pointers. Currently this issue stops me from using Richfaces 3.1.X.
I forgot to mention that there are no validation errors, and all JSF phases are properly executed. So I have absolutely no idea why the bean attribute is set to null. The attribute is not bound to any other page element, and as I said, the same code works with RF 3.0.1.