Don't know why it was on that website SeraWolf, but I am sure a member there likely got by calling Xbox Support on the phone.
So the updated steps we have that have already been mentioned to some degree around the Xbox.com forums are:
1. Turn off your Xbox 360 Console.
2. Disconnect any storage devices from the console such as the Hard Drive and any Memory Units
3. Turn on your Xbox 360 Console. See if your audio is working.
4. Re-attached your Hard Drive. This will then restart the console
5. Check again if your audio is now working.
In addition, please make sure that you have tried doing the troubleshooting steps in the below support article.
http://support.microsoft.com/kb/907605/en-us
Let us know if this helps to resolve your issue.
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