Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache and

• Remove Cookies
  Warning ! ! This will log you out of sites you're logged in to.

Type about:preferences<Enter> in the address bar.

• Cookies; Select Privacy. Under History, select Firefox will Use Custom Settings. Press the button on the right side called Show Cookies. Use the search bar to look for the site. Note; There may be more than one entry. Remove All of them.
• Cache; Select Advanced > Network. Across from Cached Web Content, Press Clear Now.

If there is still a problem, Start Firefox in Safe Mode {web link} While you are in safe mode;

Type about:preferences#advanced<Enter> in the address bar.

Under Advanced, Select General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?

Then restart.

Fred, thanks for the suggestions and sorry for the late response. Unfortunately none of these things solved the problem. Also now my previous work around as noted above no longer works either so there is no way I can get any sound out of Firefox. All other browsers IE, Chrome work perfectly. This is getting frustrating! Any help is appreciated.

I've called the big guys to help you. Good luck.

Fred, I thought i would mention that I was playing around with the volume mixer when the problem started. interestingly when I tried to play a video on Firefox this morning and again no sound, I checked the mixer and it indicated Flash Player as muted. I unmuted it and then the name changed to Mozilla Firefox but still no sound. So it seems to be related to Flash in some way.

Fred, I connected my laptop to an external monitor and the sound started playing through the monitor's internal speakers. On the volume mixer it shows the monitor listed as the device playing. Normally I play the sounds via a USB DAC and external desktop speakers. It is these that are not working along with the laptop's own speakers when the others are not plugged in. It seems to be something to do with the device selection on the volume mixer but only with Firefox?

Ahh, problem almost solved. Open the mixer. I think it can be selective as to what device has what settings. Check it out.