You have not mentioned what all you have done nor have you mentioned what you meant by the kitchen sink. So let us start with the basics Can you please check if you are able to play YouTube videos in [https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode safe mode, aka troubleshooting mode]. To go to Safe mode use the following path Menu > Help > Troubleshooting Mode. If it works fine then there is a problem in one of your extensions. Start by disabling your extensions one by one see what solves the problem. If it does not work then the Firefox browser or one of the codecs might be corrupted. Then in that case you have to uninstall Firefox completely. Before you head to add/remove programs do the following. 1) Go to Menu > Help > More troubleshooting information Copy the path of the '''update folder''' and '''profile folder'''. put them somewhere in a text file. 2) Uninstall Firefox. 3) Restart your windoze system. 4) Open explorer and go to the update folder that you kept in Step 1. and delete all the files under it. Do the same for profile folder. The value of profile folder will be something like the one given below C:\Users\<User>\AppData\Roaming\Mozilla\Firefox\Profiles\XXXXXXXX.default-release The <User> will be replaced by your user name. The value of '''XXXXXXXX.default-release''' will be different for you. We are interested in the path C:\Users\<User>\AppData\Roaming\Mozilla\Firefox\Profiles\ Delete everything under Profiles. This will make you loose all of your bookmarks, settings, passwords, etc. So back them up before doing this. If you use multiple profiles then do this for all the profiles and then delete everything under Profiles folder. Then go to C:\Users\<User>\AppData\Roaming\Mozilla\ and delete the folder Firefox. 5) Reinstall Firefox browser and check if the issue is still occurring.