ubuntuforums.org/showthread.php+youtube

I kind of fixed it anyway....but not 100% it seems. So I will go
through that one too.

I've too encountered this problem. For me, I've found the problem to
be the volume setting in MPlayer resetting it's self to 0 on it's own.
It effects the entire system. I just open MPlayer and turn the
volume back up.

My teens have been reporting that they are having trouble with youtube
and myspace the last few days. Everything was working fine til then.
Could it be them?

Why not try putting a CD in you box and see if it plays? Download a movie and
see if it plays, too. Goto MSNBC.com and run a streaming video, do you hear
the sound? Is there a volume control on one of the spearkers? If so, check to
make sure that it is all the way up. Answer these questions and you should have
a clearer picture of your next diagnostic move.

Sound from cd and sound from a site has nothing to do with one another
usually. But try that first....

Then go to System-Preferences-Sound and see if the box next to "enable
software sound mixing" is crossed. If it is take the cross away. That
might work.

And if it does not you could try this:
sudo ln -s /usr/lib/libesd.so.0 /usr/lib/libesd.so.1
sudo mkdir -p /tmp/.esd/
sudo touch /tmp/.esd/socket

Now my sounds works and I had the same problem. Thing is that when I
tried those three commands last night it worked fine after. Then today
after starting the computer up again it didn't and then I un-crossed
that box and it works. However, I haven't re-started since so i may have
to do it all tomorrow....only take a few seconds though.

Well, I questioned them further and found out that when it happens, ALL
the sound goes-and a restart fixes it, so its probably Mplayer turning
off the sound-like someone was saying.

It appears that the reboot (warm of course) can post all the hardware to the
system. THere must be a timing issue when it is cold boot and the sound card
isn't getting posting into the system or there is a dependancy that is taking to
long to develop. There could possibly be an IRQ descrepency that is taking some
time to resolve itself during cold boot and is not there during the warm. Good
luck finding that one, they are tough to find. One such trick is to move the
sound card if it is located in a slot on the PC. If it is built-in tougher to
manage.

How do you find correct settings to run your sound system? I'm looking
at "System Settings/Sound System" and I get no sound. "Enable the sound
system" is X'ed, and on the Hardware tab, "Autodetect" is showing, but it
isn't working.

Is there someplace in Kubuntu similar to Windows' "Hardware manager"?

what kind of card / computer do you have?

Do you have a little speaker on one of the task bars with a red X next
to it? Sometimes, maybe all the times, the system will boot muted...
and that is assuming you have a card that is supported and the driver
is installed... right click on the speaker and choose "Open Volume
Control"... what do you see? If there are no sliders that make sound
work, try opening Edit>Preferences... you may be able to select some
other tracks to make visible and they may allow you to unmute the
sound.

If that does not help, try to provide the type of card, is it built in
or in a PCI slot... what Kubuntu version are you running... more
details good

It may that the sound is muted. Just right click on the icon and scroll down to
Mute. If the red X is still there. Please let is know if you are using on board
sound or a sound card. Ir sounds like it is on Mute or turn all the way down.