I have found the problem. I dropped an updatable view, then I recreated the view and the triggers, all in the same transaction. It has been working well in FB 2.0 and 2.5.0 for years. Now I see that it does not work in FB 2.5.1, maybe it is a bug, I am not sure. In any case I have solved it adding a commit between the drop and the recreate. It is not the optimal solution because the database can stay in an inconsistent status but for now it works fine.
Thank you
