I know it's been a while but I had this too and found I had to:

Right Click on the RealityInstaller.app and select Show Package Contents, Then Navigate to Contents/MacOS and Right Click on the RealityInstaller and select Open so that the installer runs from the terminal.

as detailed here:

http://preta3d.com/forums/viewtopic.php?f=28&t=1124&p=7380

This has probably been caused by a change Apple made to OSX that the installer creation software didn't get updated to fix.