Make sure you are not blocking content.

Start Firefox in Safe Mode {web link} by holding down the <Shift> (Mac=Options) key, and then starting Firefox.

A small dialog should appear. Click Start In Safe Mode (not Refresh). Is the problem still there?

One issue that seems more common lately is Firefox's Tracking Protection feature. When it is blocking content in a page, a shield icon will appear at the left end of the address bar next to the padlock icon. This article has more info on managing this feature: Tracking Protection {web link}

Hi,

The problem persists when in safe mode. Same with the tracking protection, that I've disabled to run a test... Problem's still here.

Thanks for trying to help :)

Start your Computer in safe mode with network support. Then start Firefox. Try Safe websites. Is the problem still there?

http://encyclopedia2.thefreedictionary.com/Linux+Safe+Mode Starting Any Computer In Safe Mode; Free Online Encyclopedia

Hi FredMcD, first of all sorry for the long time to answer.

I tried to run in safe mode, and it is a bit better: the sound distortion is not as bad and my firefox isn't freezing completely, however I still have some stuttering and the audio gets out of sync with the video.

Anw clues what might cause this? I'm really out of solutions here... Thank you for your time :)

With 'some' improvement in Computer Safe Mode means that one of the other programs on your system is causing the issue.

See if there are updates for your graphics drivers https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration

As a test, disable your protection programs.

So, there's no update for my driver (I'm using a Nvidia GeForce) but I'll try to re-install the driver to see if this helps.

i also tried to turn off my protection program (Avast and ZoneAlarm) and no changes were made.

I called for more help.

This is not a cure, but should let the web page load without crashing.

https://addons.mozilla.org/firefox/addon/disable-autoplay/ Disable HTML5 Autoplay by Afnan Khan Firefox 55+ Disable autoplay and preloading of HTML5 video and audio players.

https://addons.mozilla.org/en-US/firefox/addon/flashblock/ Flash block Never be annoyed by a Flash animation again! Blocks Flash so it won't get in your way, but if you want to see it, just click on it

or

You can set this pref; media.block-autoplay-until-in-foreground = true

Type about:config<enter> in the address bar. If a warning screen comes up, press the I Accept the Risk button. At the top of the screen is a search bar.

Hi,

I couldn't use flashbock on my firefox, nor I had the media.block-autoplay-until-in-foreground pref in about:config; but enabling Disable Autoplay on Youtube (which I had disabled) solved my problem.

Allowing the media to fully charge before launching it seems to prevent it from crashing, so I hope this solution will be permanent!

Thanks a lot for your help!

Glad to help. Safe Surfing.