Possible Duplicate:
Youtube - couldn’t load plug-in
This just started happening on both, Chrome and Firefox, the Flash plugin simply does not work. Here is an image:
I tried changing Youtube to the HTML5 mode with no luck. Tried reinstalling the flash package or the Ubuntu restricted package with no luck. Tried disabling the plugin just in case in both browsers and then enabling it, no luck.
This is affecting both 12.04, 12.10 and even 13.04. Tested on Firefox 18 and 19 and Chrome 24 and 25.
