Flash version 10.3 now has a local control panel for managing "Flash cookies". These are identifying strings, like browser (web) cookies, that can be used to track you across sessions or record settings information. Previously it was really difficult to see and manage this separate set of cookies.
I run Windows Vista 64-bit and I was puzzled that my Flash 10.3.181.26 install didn't show anything in Control Panel - then I checked carefully and realised there is a 32-bit Control Panel icon.
Note: Unlike Vista, Windows 7 64-bit does not separate the 32-bit control panels, the control will show in the main window as Flash Player (32 bit).
Here's the Windows Vista Control Panel icon
the 32-bit Control Panel items I have
and the Flash Player Settings Manager
You probably want to look at Local Storage Settings by Site, Remove any you don't want, and then set it to Ask me before allowing new sites.