These can be set by the flash app or flash ad network and are outside of the browser security policies for cookie management. You can’t delete them from the browser since they are not stored in the browser temp directories
Go to the Macromedia site (look for shared flash objects).
There you can launch their Flash server inspector that displays your flash cookies and gives options to delete them.
Otherwise, you need to go to your Document and Settings, Applications,Macromedia,Flash subdirectory.
Here you can delete them. Make sure you set the Folder to “show hidden files and directories”

You CANNOT prevent these cookies from being written to your PC to my knowledge.
They are written when the Flash player launches.

Seems a great way for Ad networks to track Flash advertising in a more persistent manner.
I checked using SNORT on a video website displaying Flash content.
Half way into the play, Google ghost text ads (with URL redirect on click) started to appear.
SNORT showed the traffic of dynamic texting coming into the Flash content and click tracks going back to Google.
Doubt if the video site even knew this was happening.

Can’t get away from advertising. AdBlock, by the way does not work since the content played is not viewed as advertising to begin with.