Youtube stopped working due to I believe the adobe flash player. When clicking on error message, it stated this could be caused by not having the latest versions of flash and/or java. To resolve the issue, I uninstalled all adobe products including reader, flash, and air, and shockwave. I also cleared my cache. I 1st reinstalled flash, but still nothing worked. I then went to java site, and installed latest version of java. After it was installed I had to select enable the run time. After that, everything worked again. I normally only update flash player, but this happened after I updated reader. However, maybe it was just that java was being blocked since I had an older version.
I was watching a security show on ROKU, they said that Java and Flash account for a large portion of flaws. I browse with Chrome and keep Firefox handy because I run into problems all the time... if both of those don't work then I assume the trouble is not on my end. Probably it's time to wipe the hdd and reinstall everything from the ground up. I do that every so often. I can do the whole thing in a couple of hours while reading a book...
a full wipe is the last refuge of the ignorant. i have too many installed apps and customizations to do that more than once every 5 or more years. and usually when upgrading op systems to boot. a well maintained Win7 box should never need to be reinstalled.
Usually when youtube doesn't work for me it's because the browser's Flash Player plugin has crashed. But I have also had problems with youtube right after a browser version upgrade as well. I usually use Chrome but when it acts up, I go back to Safari.