OS: Windows XP
I found a solution that worked for me here:
"Launch Windows Task Manager (Ctrl + Shift + Esc keys). Click the Processes tab and scroll down and select the plugin-container.exe line. Right-click on it and select Set Priority --> AboveNormal and then exit."
Thank you for posting back with your solution. Would you mind opening a bug report at bugbase.adobe.com with the info from both of your posts? You have excellent info here and I'd like to make sure the right people get to see this. Once the bug has been added, please post back with the bug number and I'll follow up internally.
Ah, so the plugin-container is what causes this... Well, the solution jjxp2012 posted didn't help for me, so I completely disabled the plugin container (by setting dom.ipc.plugins.enabled to false and dom.ipc.processCount to 0 in about:config), which solved it (finally).
Vipiish, how has that been holding up for you? The solution I posted only worked for me to some degree, after some time the screen on youtube would freeze when scrolling when video was playing, this became intolerable quickly. So some minutes ago I went here:
and downloaded an archived older version 10.3.183.68 (Released 3/12/2013). This is working perfectly on FFox so far. It seems any version starting with number "11" is a problem on XP in any browser.
Unfortunately the solution I posted with the Task Manager created another problem so I had to abandon it. Not sure if it may help someone else though. I tried swithing to Chrome but had similar garbage happening: popping and interuption to audio when pages would load, when scrolling very fast or even mouseovering on abjects. What I had to do as I explained in the reply to Vip, is install a different version of flash 10.3.183.68 (Released 3/12/2013). I had to do a similar thing months ago when 11.3 came out and created the same problems. Hopefully I can hang on to this version (10.3.183.68) for a while as it seems to work perfectly.
I'm on Flash 11.6 now and still have the plugin-container competely disabled. Everything has been working fine!