I am running the lastest version of Safari on Mac OS X 10.8.2. Since I updated my Mac I have been unable to view any video content on the web (Youtube, etc). "Blocked Plug-In" appears in the video box and I have tried many times to install the latest version of Flashplayer. When I go to information in system preferences it says that I do have the latest version installed (11.5.502.110), but the same message appears when I try to use it. I have uninstalled and installed Flash and restarted my computer numerous times. I am not sure what to do in order to make this work.
Could you please check the Library > Internet-Plugins folder in Mac?
Ideally, there you should see Flash Player related files after a successful installation.
If you see the files, ensure that Flash Player is enabled in Safari.
Go to Safari Settings > Security and select Enable Plugins.