This is either a compatibility issue or a program error. I recommend keeping only a version of Adobe Reader installed on your computer, because if you have two applications that do the same thing, issues might appear. Secondly, there is the possibility that Diaform+ lacks compatibility with the OS or with one of the Adobe versions. Try installing the latest version of Diaform+ and Adobe Reader and then observe the functionality. If you still have issues, try different ways of launching Diaform: in compatibility mode or with Administrator access.