All of a sudden our desktop won't open PDF files (Windows 8.1 I think)

When I click on a PDF file, A small box comes up with a big red "X" and it says

C:/Users/Pam/Downloads/(file name).pdf
Invalid value for registry

Does this have anything to do with the Heart Bleed thing? Or windows changing stuff because they're not supporting XP? Or is it just windows 8 being stupid?