Symptoms

Error on K2 Designer:

Server Error
Unable to load one or more of the requested types. Retrieve the LoaderExceptions property for more information.
Could not load file or assembly 'Telerik.Web.UI, Version=2012.3.1017.0, Culture=neutral,...' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference.
 

Diagnoses

The Smartforms Control Pack was not upgraded along with blackpearl and smartforms.
 

Resolution

Upgrade the Smartforms Control Pack to match the other K2 components installed