Ok, so when 11.3 first released my system asked me if I wanted to update. I told it yes, it updates and I re-open my browser (was using Google Chrome at the time). I go to play a facebook game and suddenly my system lags immensely to the point I almost thought it had frozen. The moment I closed the window with the FB game, my system ran fine. I have the same experience using Firefox and also while doing things like watching Youtube videos. So I downgrade to 11.2 and boom....zero issues running the exact same games (though I have switched to back to Firefox since Chrome autoupdates Adobe flash to 11.3 and yeah....it gives the same issues I just described).
So its been like a few weeks or whatever since 11.3 has released and I "fixed" my issue. Adobe flash updater pops up saying there's an update. Without thinking (since I like to keep my programs up to date, especially to prevent security issues) I tell it to update until I see the version number is 11.3 and I remember the issues I had. Hoping to the computer gods that maybe it has been fixed I load up a Facebook game...and get slammed in the virtual face with severe lag...guess its time to downgrade once again...
Try if updating your graphics drivers helps; see http://forums.adobe.com/thread/945765
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