I had a strange (at least to me) issue. I’ve created an ASP.NET or silverlight applications on the file system (using the Web Development server as the Web server). When I ran the application, the browser showed it cannot find the web site. The url looks like: http://localhost:53467/WebSite1/Default.aspx
First I suspected an IE/firefox issue, but no change there.
Then I tried to replace localhost with 127.0.0.1 and it worked! Very strange.
Even stranger, using localhost with no port (i.e. port 80) worked (IIS serviced the pages correctly).
Then I though of firewalls, anti virus and such. Nothing worked.
Finally, I looked at the hosts file in System32\Drivers\Etc folder, and there I found this:
What was that ::1? No idea really. I removed that line, saved, and presto: all back to normal!