We reccomend that you have a broadband internet connection in order to play the video files.
You might not have a new enough version of the Flash player installed. Visit http://get.adobe.com/flashplayer/ and download the newest version, then try again.
You might have software on your system that will not allow videos to play at your school. If so, you'll need to disable it in the library or download the free videos from the iTunes store and keep them on a computer where kids can access them. Search keywords Skeleton Creek in the iTunes store to find the free video podcast if you want to go that route.
Re-load your page. Sometimes the servers do get hit with a lot of traffic at once. Refreshing your browser or coming back later can help.