Running ASP.NET MVC 4 with HTTPS under IIS 7.5. GET request works fine as long as server completes request within 5 minutes. For longer requests, however, IIS appears to be sending 401.2 at EXACTLY the 5 minute mark (consistently - 5 MINUTES).
This yields login popup in IE. If user enters login info, server logs indicate that a NEW request is started. (Same behavior in Firefox [401, etc], although no login popup -- must be automatic).
The original request actually DOES complete on the server, but it is effectively lost.
Both Negotiate and NTLM auth providers are enabled. (I did try using Negotiate ONLY, but that did not seem to make a difference). There does not appear to be any kind of timeout going on anywhere.
Why the 401? Why does it happen at 5 minutes exactly?