We had a development track with InfoPath (I’m not going to comment on how long the project was, but it was long 😉).
We deployed to UAT without any IE version issues, then deployed to production. That’s when the fun started.
The Problem
With NTLM/Kerberos and IE 6.0 + InfoPath Form Services, users navigating to the site got a logon prompt. After filling in their username, password, and domain three times — nothing. A blank white page.
Environment: mixed — Windows 7, Windows XP, and Windows 2000 Professional. Joy.
What We Tried
Step 1: Switch from NTLM to Kerberos
Some success — 30% of users reported the problem was fixed. The rest still had blank pages.
Step 2: Framework versions, IT settings, IIS configuration
Other machines with the same settings worked fine. Nothing stood out.
Step 3: The actual fix
A colleague checked an IE setting: Enable Integrated Windows Authentication.
Everything was fixed immediately 😊
We had noticed this setting early on but dismissed it because other machines had it unchecked and still worked. Too hasty.
The Lesson
Occam’s Razor applies here: the simplest explanation is usually the correct one.
When debugging authentication issues with IE + SharePoint, always verify Tools → Internet Options → Advanced → Enable Integrated Windows Authentication is checked before going deep into Kerberos SPN configurations.