Use the Activity Monitor to check if Safari is still running in the background.
I did and it was not running in the background.
There are other users in this forum who know a lot more about Mac OS than I do, but until they come back later, I suggest that you restart your Mac, then run the Flash Player installer before doing anything else.
Download the offline installer here: http://fpdownload.macromedia.com/get/flashplayer/current/licensing/mac/install_flash_playe r_11_osx.dmg
If it won't download directly, right click and "Save as"
Go to: Mac HD/Library/Internet Plugins
Trash the Flash Player.plugin file from there
Go to: Mac HD/Library/Application Support/Adobe
Trash the Flash Player folder (the whole folder)
Empty the trash
Mount the DMG and run the installer.
BEFORE opening any Flash content in Safari, open Safari>Preferences, and check the Security tab to make sure "Allow all other plugins" is checked.