I have a Mac, and I can't watch the videos. Thanks for writing. Unfortunately, we don't currently support Real or Quicktime for Macintoshes. In particular, the embedded version of RealPlayer is a sticky platform on the Mac. Our system definitely does work for some Macs, but we've seen problems in others, and we generally don't have too much support available for Macintosh users here.
Quicktime support is still under development.
I've tried all that, and I'm still having problems.