I've got the new r75 today, and was really looking forward to the new Family feature. But even though the browser preview works fine, I get this window when I try to export the project:
This bug should be pretty easy to reproduce, as it happens regardless of the family name or the objects inside it. It still happens even if there are no events using the Family. I'm using the "Export for HTML5 web site" option when trying to export the project.