I've also starting having some awful performance hitches involving Flash, which might be related. Sometimes if I watch a Youtube video, the whole browser window (not just the current tab) locks up for a few seconds. Just started happening a few days ago, on Chrome for Mac.
As I said in my last comment, Chrome has its own built-in Flash Player. Even if you have another player installed on your machine, the built-in one overrides it unless you specifically disable it.
If you have another Flash player installed, go to chrome://plugins and disable the one that was installed with Chrome. It's obvious by the 'Location' which one this is, at least on Windows. I don't have a Mac so I can't help you there.
It's possible that this is just a problem with Flash 11.3. When I was having the video issues a few weeks ago, I installed the newer 11.4 version. Chrome's built-in player still calls itself 11.3. I don't know if it's that Flash Player version that's having the issue, or Chrome's built-in version specifically. My only specific complaint was that Chrome 22 re-enabled the built-in player without my consent.
