Run the Flash Player Uninstaller as applicable for your machine(i.e.Windows or MAC) and remove flash player.
Restart the machine.
Download and Re-install Flash Player.
Restart the browser and check.
You might also wanna check the below articles ::
Enabling Flash Player in Internet Explorer 9 : http://forums.adobe.com/thread/885448
ActiveX Filtering in Internet Explorer 9 : http://forums.adobe.com/thread/867968
[topic moved to Flash Player forum]