I've upgraded two devices to the Windows 8.1 Preview - a desktop and a Surface Pro.  On both these devices, I am no longer able to log into a Citrix landing page successfully.  In order to get to a login prompt using IE11, I have to add the landing in Compatibility Viewing (no big deal), but any attempts to log in (using two stage authentication including an RSA key) fails with:

"The credentials you typed are incorrect. Please try again or contact your help desk or system administrator."

I figured this was an IE11 issue, so I started adjusting the usual suspects.  The page was added as a trusted site, disabled Enhanced Protected Mode, as well as (temporarily) setting all security settings to its lowest value  No change.   I used the same login on another device for verification and connections work as expected.  Logins using the landing page worked normally on both of these devices prior to the 8.1 preview. 

At the recommendation of our Citrix administrator, I installed "a alternative browser" to eliminate the IE11 variables - while the landing page worked without any compatibility settings, the same error returned upon entering the same credential set.  I'm guessing this is a change at the OS level.  I did the rounds with Bing to see if anyone else had seen this and determined root cause, but I'm apparently the only one with this condition so far.

I did see that there were changes in 8.1 on how VPNs work (applications can pass VPN  requests directly to the OS), but I can't find out where to set/modify these settings.

Citrix is  4.x without a published storefront (security compliance thing).  This fails during authentication - the Citrix Receiver hasn't launched yet.   I've seen similar problems reported for Cisco and Juniper VPNs, but I don't have the network adapter listed in the fix.

Suggestions/links/docs?