I have had repeated trouble installing Flash Player 11.8.800.94 on Mac OS X 10.7 (Lion) despite following every step listed in the Macintosh Installation Help guide: uninstalling previous versions, turning off anti-virus protection, etc. Each time I get a warning message for both Safari and Firefox attempted installations as follows: "Error: General installation error." The only solution seemed to be to reinstall an earlier version: 11.7.700.225.
If you're not comfortable with terminal commands:
Download the offline installer here (right click and "Save as")
Quit all browsers
Go to: MacHD/Library/Internet Plugins... and if the Flash Player.plugin is still there "trash it".
Then go to: Mac HD/Library/Application Support/Adobe and "trash" the Flash Player folder if it's still there.
Empty the trash.
Mount the DMG and run the installer
Relaunch Firefox and it should work
The procedure using the terminal commands as suggested in the link blueskyworkshop worked and Flash Player was successfully installed in Safari, Firefox, and Chrome whereas using the offline installer did not. Also, I uninstalled the previous version of Flash Player using the uninstall app and then restarted before attempting a new installation.
Thanks for your help, C F McBlob!