Huh. It turns out that the HTML5 versions of the podcasts do play in Internet Explorer v9 and the problem was mine all along (I hate that!).

I have been working on the problem of my not being able to see the podcasts since I started using the HTML5 tags and I’ve searched the web for clues since the beginning (about 9 months). I finally accidentally stumbled upon the problem. It turns out that there are some problems when running Internet Explorer v9 virtually in VMWare Fusion v3! I don’t have access to IE v9 at work because we’re on v8 so I’ve been doing this with my own machine.

Sure enough, when I reboot my Mac using Boot Camp, they worked! More digging turned up the real problem. I have to disable 3d graphics hardware acceleration in the VMWare settings and then the HTML5 video works.