If you have problems with current Shockwave Flash plugin versions then check this:

• see if there are updates for your graphics drive drivers

https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)

https://forums.adobe.com/message/4468493#TemporaryWorkaround

• disable hardware acceleration in the Flash plugin

https://forums.adobe.com/thread/891337 See also:

• http://kb.mozillazine.org/Flash#Troubleshooting

FredMcD said

If you have problems with current Shockwave Flash plugin versions then check this:

• see if there are updates for your graphics drive drivers

https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

• disable protected mode in the Flash plugin (Flash 11.3+ on Windows Vista and later)

https://forums.adobe.com/message/4468493#TemporaryWorkaround

• disable hardware acceleration in the Flash plugin

https://forums.adobe.com/thread/891337 See also:

• http://kb.mozillazine.org/Flash#Troubleshooting

I did everything you told me to, but the problem is still there. Firefox 41 skips the first second of all MP3 files. I have to stream the same MP3 file twice if I want to listen to the first second of any MP3 file. If I close Firefox and reopen it, the problem appears again.

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

FredMcD said

Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox. Is the problem still there?

Yes, I restarted Firefox in Safe Mode, and the problem is still there.

Start your Computer in safe mode with networking. Then start Firefox. Try Safe web sites. Is the problem still there?

Starting The Computer In Safe Mode;
Free Online Encyclopedia

I assume that Firefox uses the HTML5 media player to play the MP3 files.

Is only the first second missing?

This could be a problem with the volume setting.

cor-el said

I assume that Firefox uses the HTML5 media player to play the MP3 files. Is only the first second missing? This could be a problem with the volume setting.

Yes, only the first second is missing. It could be an html5 issue. I don't know. All I know is that Firefox, my favorite browser since 2007, keeps disappointing me with every new update. Every update instead of solving existing problems, creates new ones. If in the next update the problem is not resolved, I'll delete Firefox and I'll start using Chrome exclusively. Thanks a lot for your time, both of you.

Can you hear that first second if you drag the slider back to the start?

cor-el said

Can you hear that first second if you drag the slider back to the start?

Yes, I can hear it. It's the only way to hear the first second. If I close Firefox and reopen it, then I will have to drag the slider back to the start again.

The new update (Firefox 42) solved the problem. Thank you very much.