At this URL I have HTML5 video and audio elements both set to autoplay but it appears as though only the video is auto-playing.
Clicking on the thumbnails should start up a new video as well as a new audio file but I am only seeing a response from the video element.
This page is being developed in FF 3.6 for now.
http://jeromecovington.com/jrm/somaset
Click anywhere on the expository page with the quote to see the problem I'm having.
With Chrome 5.0.375.126 on MacOSX 10.5.8 on my Mac laptop, I can't reproduce the problem -- video and audio both work simultaneously as predicted. Same with FF 3.6.8, same platform; and, I can't see any problem with your page's source code, either.
What exact release of FF 3.6, and on precisely which platform, are you using to reproduce the problem? I wonder if it could be a FF bug (on your specific release/platform combo) in what is, after all, still pretty new functionality (can't expect it to be as stable and robust as older, solidly-developed parts of that generally excellent browser, I guess!).