No sound when using BBC iPlayer or youtube.

I have just built my first Ubuntu (Intrepid) machine and have been completely bowled over by its speed and ease of use, particulary for someone, like me, who has never tangled with LINUX before. One tiny problem is bugging me however. I am a frequent user of the BBC iPlayer site. I can get to the site without a problem and can play back TV programmes, however, although I can see the programmes I cannot hear them. I have also noticed that the same problems occurs on the Youtube site. I know that my sound card is operational, because I can play (and hear) MP3s. Is there someone, who has used Ubuntu longer than I, who knows why I encounter this problem?

N.B. I am a complete newbie. but, the common factor would appear to be Flash.

what flash player are you using? flashplugin-nonfree is the official adobe plugin, i've never had problems with it not playing sound, but it does have problems with focus, in browser (ie it takes focus and u have to click elsewhere to get it back) and it used to not pay attention to z-order, although it seems to now.

I'll assume your sound is working elsewhere just not in the flash player? Make sure nothing else is using sound in a terminal run:
sudo fuser -v /dev/dsp*
sudo fuser -v /dev/snd/*

and it'll tell you if anything is, (you can ignore sequencer and the mixer_applet program)
you can probably ignore pulseaudio as well, but if nothing else is using it (of course ignoring the ones I told you to ignore) then try 'killall pulseaudio' in the terminal.

If that doesn't work , uninstall flashplugin-nonfree, and try mozilla-plugin-gnash
If that one doesn't work try swfdec-mozilla

On You tube flash sounds works for me sometimes.
Below are the details when it works.

terry@terry-desktop:~$ sudo fuser -v /dev/dsp*
[sudo] password for terry:
terry@terry-desktop:~$ sudo fuser -v /dev/snd/*
                     USER PID ACCESS COMMAND
/dev/snd/controlC0: terry 6170 F.... pulseaudio
/dev/snd/controlC1: terry 6170 F.... pulseaudio
                     terry 6284 f.... mixer_applet2
/dev/snd/pcmC0D0p: terry 6481 F...m firefox
/dev/snd/timer: terry 6481 f.... firefox
terry@terry-desktop:~$

The last 2 lines are not evident when flash sound is not working.
I run Ubuntu ls Hardy

I'll take it by the second to last those last two lines are changed but still there when its not working?
Basically what that means is that something else is using the sound. For some reason your flash plugin doesn't want to run through pulseaudio and is taking a direct connection to the device instead, if some other program were to do that first, it wouldn't get a connection. So basically you have too fixes, a short term and a long term. Short term you could just run that command, find out wats using /dev/snd/pcmC0D0p and close off whatever program is using it, then firefox/flash plugin can use the sound again. However a better more permanent fix would be to configure the flash plugin to route its sound to pulseaudio.

Basically to do that theres two ways. 1) upgrade to intrepid, that would fix this problem straight away as flash is configured to route to pulseaudio from the start XD
2) take a look at the section about hardy at this link http://ubuntuforums.org/showthread.php?t=789578