look at your code... you have set autoplay=true when the playlist is empty at pageload.
Press F11 then select the Script tab, place a breakpoint on the player function then press the 'Start Debugging' button.
If you are satisfied that it is not your coding then please submit an issue report.
Yes it is BETA.... I know its not RTM.. I know there are some real woozies in IE9 Beta that have to be fixed yet. You can submit issue reports at connect like other MSFT or Public 'testers'. Connect won't reply with a detailed response of why or why
not either.. If it works it works... if it doesn't, it hasn't been fixed yet or it is not in their mission statements (see Help>Whats new in IE9).
The Fat lady hasn't even stepped up to the podium yet.