And what problem does it report? Reporting any error messages displayed will help the Filemaker techs better understand what went wrong.
FileMaker 12 is not tested on 10.8
With that said........ I can confirm it works just fine. So, as Mr.ModJunk already said a little more info would be helpful.
I have a question for you though, are you able to edit posts on this forum in safari on 10.8 because I cant.