Hi, there's an addon for Firefox that lets you block and delete flash cookies here https://addons.mozilla.org/en-US/firefox/addon/6623.
You can also delete them manually by going to C:\Users\[Username]\AppData\Roaming\Macromedia\Flash Player\#SharedObjects\[Some random text]\ and selecting which cookies you want to delete.
Flash cookies aren't necessarily a bad thing. By deleting them, you may delete useful data, such as saved game data from online flash games.
