I am experiencing the same problem. I have no sound/audio on either FireFox
2.0.0.6 or IE7. I have downloaded and installed the most current Flash Player
(version 9.0.47.0) This just started happening recently within the last few
days. I haven't added anything new to my computer, at least to my knowledge.

On the Mac side, try this technote:
"Flash Player audio failure on Intel-based Macintosh"
(http://www.adobe.com/go/41f8f08d)

On the Windows side, I thought at some point a few months back we were
developing a Windows audio troubleshooting technote. But now I don't see
anything internal about it. :(

So I'll throw out some random tips gleaned from searches:
-- In your registry:
My Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
NT\CurrentVersion\Drivers32
Create a new String value named ?wavemapper?. As value give it
?msacm32.drv?.
-------------------------------------------------------------
1. Go To Control Panel
2. Then Sounds and Audio Devices (Default Control Panel) or Sounds Speeches
and Audio Devices then Sounds and Audio Devices (XP Control Panel)
3. Then go on Audio
4. Then First one Under Title Is Sound Playback Then Under That Is Default
Device Then make Sure That This Is Your Sound Card.

Some users have is "SB X-Fi Audio [EA00]" or some other value. The value
should be "Modem #0 Line PlayBack"

Sorry, that's all i've got for now.

From that technote:

B.Wolf,
I went to the website and it asked me to change"Audio MIDI Setup, select
sound output and change the properties for the 'Built-in Output' to a setting
less than or equal to 48Khz." That option is not available on my computer. It
also suggests "I upgrade to Flash Player 9.0.20.0 resolves this issue." But, I
already installed Flash Player 9,0,47,0 installed.

OK on OS X 10.4.10 you should have the following path when logged in..
<mac name>:<hard drive name>:Applications:Utilities
There should be a utility named "Audio MIDI setup". If you have trouble
finding it, search for it using Spotlight.

There are -many- confirmations of this fix
(http://fredericiana.com/2006/06/14/flash-video-and-no-sound-on-osx/, for
example).


Other people have reported other things that have worked as well..
-- simply launching Garageband (resets audio output to 44khz)
-- deleting the "Macromed" folder from <user>:Library:Preferences
-- double check that Audio output is going to built in speakers or headphone
jack (again in Audio MIDI Setup utility)

I had a problem at first because the option for audio output was not available.
That is because I had Properties setting for iSight. But, when I changed it to
built-in audio, I was able to changed the settings. IT WORKED! Thanks a lot. I
was beginning to think that the problem would only be solved by getting Leopard.

In the last few days, I lost sound on most websites. For example, I have no
sound on CNN, abcfamily.go.com and You Tube. I have sound on
http://dynamic.abc.go.com/streaming/landing and http://video.cwtv.com/ (which
may not use Flash). I have the exact same problem using both Firefox and IE7.
I have a Dell Dimension E520 running Windows Vista. I am using the most current
Flash Player (version 9.0.47.0). The registry settings in my computer appear to
be correct. Dell technical support gave up, and told me to re-install the
operating, which I am not going to do. I am wondering if a recent upgrade of
iTunes may have broken Flash Player. Many people recently appear to have the
same problem, which indicates to me that some recent upgrade or patch broke the
Flash Player audio. This looks like a good opportunity for Flash competitors to
take market share because You Tube and other websites that depend on video need
reliability. It kind of reminds me of how the buggy Microsoft web browser lost
market share to to the more reliable Firefox browser. Hopefully, Adobe will
release a solution or patch soon.