When you get the email, you should get a link like
http://www.civinfo.com/forum/viewtopic.php?p=5597#5597
Which of course works fine in XP etc. Where does it fail? If you paste the link into the browser, does it work? I have IE7 beta here (just for testing the forum) and it works fine in that, and I thought Vista Beta was using the same IE.
I suspect that this is Beta syndrome, there are about a trillion phpbb forums like this, so if Vista breaks it - I blame Vista! Does Vista support Firefox?
Just had a look - RSS also works fine in IE7: