Hi,
This is from Adobe itself:
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Issue
Adobe Flash Player is not supported for playback in a 64-bit browser. However, you can run Flash Player in a 32-bit browser running on a 64-bit operating system.
Reason
Adobe is working on Flash Player support for 64-bit platforms as part of our ongoing commitment to the cross-platform compatibility of Flash Player. We have not yet announced timing or release dates.
Solution
To use Flash Player to view Flash content on a 64-bit operating system, you must run a 32-bit browser.
Keywords
Vista, 64 bit, 64bit, Vista64
TechNote Details
Last Update: 02-05-2008
ID: 6b3af6c9
Permanent Link:
http://www.adobe.com/go/6b3af6c9
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So, you need a 32-bit browser, or a wrapper (nspluginwrapper/nswrapper) to use 32-bit plugins in a 64-bit browser.
Hope this helps, don't think you have a sound-issue, but a flash-issue...?