Brian, I'm seeing the same problems with the tutorial videos linked at the bottom of this page:
http://www.omnigroup.com/application...cus/tutorials/
Note that it seems the iPhone versions work fine. It's only the primary versions that either show a blank window or report the same error Karen is seeing.
I am able to view movie trailers on Apple's web site and other QuickTime content on the web. I'm running Safari 4.0.3 and Snow Leopard.
-Dennis