You seem to be running the folder named .../Flash Player Debugger.app
. What you want to do is run the binary inside that folder. My best guess it is named .../Flash Player Debugger.app/Contents/MacOS/Flash Player Debugger
.
Use Finder or some other file browser utility to show the contents of the folder /Applications/Adobe Flash Builder 4.5/player/mac/11.5/Flash Player Debugger.app/Contents/MacOS
to figure out the name of the executable file.