I am having the same problem.

When I open the html files from my desktop the ical links work fine and open in ical.

But when I open the html files from our intranet server I get what the others are getting just a text blurb in safari ... yes if I download the file to the desktop, tell it to get ride of the .txt suffix and then open from the desktop it does work...

BUT there is no way I am going to try to tell all our users to do that ....