CF,
Thanks very much for your post. I have been very frustrated with trying to install this latest version, over the past 2 weeks (it would get stuck at 95%). I finally succeeded tonight using your clear instructions above as well as an extra piece of advice that an apple genius gave me tonight.
Before you can install Flash 12, you have to ensure that any previous versions are erased from your computer.
Here is what I did:
1) I ran the adobe uninstaller to uninstall the previous Flash. Here is the link : http://helpx.adobe.com/flash-player/kb/uninstall-flash-player-mac-os.html
2) I downlowded your instructions for the "SnowLeopard Clean Install.pdf",printed them out, and downloaded the "Flash Player 12 (MacOSX) installer", as per the instuctions above. I then followed your instructions including..
3) I erased the FlashPlayer.plugin and the flashpalyer.xpt files as you suggested in your instructions above.
4) I also made sure to erase the Flash icon from the bottom row of my System Preferences window. (Advice from Genius)
5) I then used the Full installer that you suggested above, and it worked like a charm. (When I did it earlier without step 4, it did not work).
Thanks again. I am still not sure why the Adobe GUI does not work, but this work around solved the problem.