Symptoms

After adding the K2 for SharePoint Worklist web part to a SharePoint 2010 page, opening the SharePoint page takes extremely long. If one removed the K2 for SharePoint Worklist web part to a SharePoint 2010 page again, the SharePoint page opens quickly.
 

Diagnoses

Initial investigations pointed towards the identity services causing the "go-slow". Because blackpearl 4.5 with 1420 was one of the very first builds where we introduced the identity services cache, we could not "retro-fit" all fixes up to the latest release into 4.5 with 1420. There has simply been to many big architectural changes made since then.
 

Resolution

LABS gave us a "identity services fix" that addressed the issue to some extent. After applying the fix, we saw a relative increase in performance when opening a SharePoint 2010 page that has the K2 for SharePoint Worklist Web part on it.