Based on your error message, I bet it's not FF3 but whatever showed you the link. If I had to guess, you clicked on the link/page through a feed reader or something?
Can you confirm whether it happens when you click directly from this page/site on Hacker News? (which seems to be handling them great)
I'm using Firefox 3.0.5 on Windows XP.
FYI, the other link you gave in http://news.ycombinator.com/item?id=498246 too doesn't work for me: "Firefox can't find the server at www.%e0%b2%95%e0%b2%b0%e0%b3%8d%e0%b2%a8%e0%b2%be%e0%b2%9f%e0%b2%95.com."