I created the video on my iMac, and exported the file to m4v from QuickTime 7.7 Pro. From my moderator's posting log, I can see that you're running Lion, which unfortunately I've only read about; I'm still using Leopard.
I have a hard time believing that the updated version of QT for Lion wouldn't include the ability to read the AAC / H.264 codecs of the file, but again, I have no experienced with Lion.
Could it be a configuration issue? Have you tried downloading the file to your Mac and opening it with QT or iTunes?
Any Lion experts out there?
Hope that we can sort this out for you!