hi, I understand that this can be pretty frustrating when watching videos for extended periods of time. In order to troubleshoot the performance we can start with the memory warning.

Please try to watch videos in Safe Mode to make sure it is not acceleration or a malicious add on. Use Troubleshoot Mode in Firefox

Please also make sure that your graphics drivers are up to date: Upgrade your graphics drivers to use hardware acceleration and WebGL as well as make sure that you do have sufficient memory Fix Firefox using too much memory or CPU resources and Fix common audio and video issues

You can try to disable OMTC and leave hardware acceleration in Firefox enabled.

• about:config page: layers.offmainthreadcomposition.enabled = false

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

Neither of those solved the problem.

The strange thing is, it isn't actually using up too much memory, according to Task Manager. It just stops the sound on every application. I am really not sure what causes it, but only that closing firefox re-enables the sound.

Boot the computer in Windows Safe mode with network support (press F8 on the boot screen) as a test to see if that helps.

• http://www.bleepingcomputer.com/tutorials/how-to-start-windows-in-safe-mode/