My prefs just reverted...yet again, and I found that /Users/artie/Library/Preferences/Macromedia/Flash Player/macromedia.com/support/flashplayer/sys/settings.sol had been deleted; resetting my prefs resulted in the file's being recreated.
I deleted ~/Library/Preferences/Macromedia/Flash Player (the entire folder) and it was re-created when I reset my preferences. Unlike you, my preferences have not reverted to defaults. I don't know why yours did. Maybe you should delete the entire Flash Player folder?
