First, open Terminal (/Applications/Utilities/Terminal(.app)). In the new Terminal window, type \"cd \" (note the space after \"cd\"). Then, in the Finder, locate your \"Planeshift 3D\" folder, drag it into the Terminal window, and drop it there (text should appear after \"cd \"). Click inside the Terminal window and then press return.
type
\"chmod 755 pssetup.app/Contents/MacOS/pssetup\"
and press return.
worked for me.