How to open .ics files properly?

Hi-

I just experienced a strange thing while clicking on links for .ics calendar files on two different macs. On one machine it works as it should, i.e., you click on the link and a popup window asks if you want to save the file. If yes, it will then open the file in Entourage. Great. On my other mac I click on the same link and it just opens the file in its raw form, almost like viewing the source code of a web page. Does anyone know why this is so? How can I get the file to open properly on this machine?

Thanks.