Using Macos 10.8.4 on a mac mini (2012, i7).
On Safari, Firefox, Chrome or SR Iron, flash videos do not work at all. I get a "movie not loaded" message.
Going to this url
http://helpx.adobe.com/flash-player.html
Flash 11.7.700.225 reports "Movie not loaded".
Upgraded to the flash beta did not solve the problem.
Tried doing a complete uninstall, reboot, reinstall. No dice. Same issue. Cleared out all cookies. Removed extensions. Nothing worked.