I just had a weird problem - for some reason IE wouldn't run my XAF (eXpressApp Framework) web applications (ASP.NET) anymore. At first I suspected some sort of installation problem, since I'd just installed the new 8.1.1 version, and not long ago this used to work just fine. But for some unrelated reasons I uninstalled and reinstalled, and the problem was still the same.

In the URL for the application, I tried replacing "localhost" with "127.0.0.1" and I found that this solved the problem. I ping'd localhost and I noticed that it was using ::1 as the address instead of 127.0.0.1 - the IPv6 equivalent. I looked in my hosts file and there was an entry in there, combining ::1 with localhost. Removing that entry solved the problem.

Now, this is a bit weird... I actually thought I didn't even IPv6 enabled at all, which would have explained why connections to ::1 wouldn't work. But I found that it was in fact active - not sure why, I believe I switched it off at some point. Pinging ::1 is not a problem. So why can't IE connect to it? And who added the ::1 entry to my hosts file recently? Or was it previously working in spite of that entry?

Bizarre Windows network stuff... see, that's why I still love Linux for my servers. Text based config files that never suddenly change automatically. Great.