Symptoms

Recently I was given a laptop running Windows 8.1. On this new machine I am not able to open workflow *.kprx files. Same files open OK on other machines.

Error: an Item with the same key has already been added.
at System.ThrowHelper.ThrowArgumentException
at System.Collections.Generic.Dictionary2.Insert
at MS.Internal.FontFace.PhysicalFontFamily.ConvertDictionary
 

Diagnoses

A font that was installed as part of another program was causing the conflict.
The program had been uninstalled, but the font had remained.
 

Resolution

The client removed the font and now they can open K2 projects.