After upgrading to K2 Five, the K2 Management Site loads a blank page and Forms running via the 'Runtime/Runtime' URL spins continuously.
Forms do load when using the 'Designer/Runtime' site; this indicates a difference in configuration between the two sub-sites.
Unable to get property 'setAntiXSRFHeader' of undefined or null reference
It was determined that the following key was implemented in a previous version of K2 which had resulted in this behavior:
To resolve the issue, comment out the "Forms.LegacyBrowserSupport" key in the web.config file for the Runtime site.
This is usually at location (C:\Program Files (x86)\K2 blackpearl\K2 smartforms Runtime).
This is commented out by default settings and is only applicable for K2 versions 4.6.9 and 4.6.10.
K2 Five is not compatible with SharePoint 2010 and compatible with version 11 of Internet Explorer: