Flash player installer indicates installation on Mac Powerbook Hard drive is impossible?

I am running Mac OS 10.8.5 on a Mac Powerbook, with FireFox 25.0.1 (also Safari, with similar results).  I have turned off virus protection and firewall. Following directions after my first installation failure, I did a uninstall of the older version of flash player that I was using. No matter what I do (reboot, use Safari instead of Firefox, etc.),  the auto-install progresses to  "installing flash player preferences" and the action bar runs to 50%, then triggers an error message.  When using the Flash Player Install App that asks where to install flash player, it tells me that installation is possible on my hard drive. What do I do next?