Symptoms

When using IE All users are receiving the Multiple Authentication Attempts detected error. The error does not occur with browsers other than IE.
The error is occurring on the server running IE11, it was previously receiving the same error running IE9 and updated to see if IE11 would address the issue.
The SOE here is IE9, so other users are receiving the error from their desktops (windows 7). I am running IE11 on windows 10 and receiving the error too.

Tried a number of tests, including running the site using the Intranet Zone config and Trusted Sites config on both my laptop and from the Server with no effect.

There are no errors showing in the Event Log or in the K2 Host Server log. I can see multiple requests being made in rapid succession in the IIS logs.

 

Diagnoses

Unfortunately IE cannot handle underscores in hostnames:
https://en.wikipedia.org/wiki/Hostname_Restrictions_on_valid_host_names
http://blogs.msdn.com/b/ieinternals/archive/2009/08/20/wininet-ie-cookie-internals-faq.aspx

 

Resolution

The site will need to be re-bound.
Then run K2 Blackpearl configuration manager.