I asked this yesterday and received no responses, so I'm posting it again. Would very much like to hear some thoughts on what the issue is and how I might correct is, so I can update to the latest edition of Firefox. Anybody? Thanks. I was prompted to upgrade to Firefox 40 today, and as soon as I did that, I started having issues with video playback on YouTube and various other sites. The video was slow, the sound was all garbled. I have the latest version of Flash installed. Everything was working perfectly before the upgrade. Just to see, I downgraded back to Firefox 39.0.3 and the playback issues were gone. So needless to say, I won't be upgrading anytime soon. Is this likely a Firefox issue, a Flash issue, an issue with my computer? I'm running Windows XP. Any help, thoughts would be appreciated.