The error "Installed Adobe Flash Player Is Not a Debugger" occurs when you try to debug a project. Flash Pro CS5 is installed and you are using the standalone player (no HTML wrapper).
Uninstall Flash Player and run the debugger player installer found at INSTALL_DIRECTORY/players/. For the stand-alone Flash Player, launch the stand-alone Flash Player found in INSTALL_DIRECTORY/players/ and open a SWF file to reassociate that version of the stand-alone Flash Player.
This error occurs when a release version of Flash Player was installed with the Creative Suite Flash Pro installation, or by some other means.