I recently updated the flash player to v10 on my mac. It broke video playback on many websites including nickolodian cartoons (argh ironman) and our intranet at work.
I seem to remember this happening the last time a major flash update was released. I’m not sure if it is related to some other software on my machine or not.
Turns out that the upgrade didn’t work properly. The fix was to remove the flash player altogether and do a fresh install.
Flash uninstallers:
http://kb2.adobe.com/cps/141/tn_14157.html
Fresh install flash after your uninstall:
http://www.adobe.com/go/getflash
http://kb2.adobe.com/cps/141/tn_14157.html