I suddenly got a similar sounding problem, VWD with the ASP.NET Development Server has been working here always, then today I got errors in browser for all projects saying something vaguely in norwegian about it couldn't connect to server localhost. Since I haven't installed or configured anything for ages I think some kind of Vista or application update has either changed my HOSTS file or decided to no longer use ipv6 or something. Some web research got me on track to this plain text file which is in folder "C:\Windows\System32\drivers\etc", when reviewing this file it only had one mapping: "::1 localhost" where ::1 is the ipv6 loopback address, I added this line "127.0.0.1 localhost" for the ipv4 loopback address and the ASP.Net web sites was loading again.
