Symptoms
Workflow does not proceed after user actions task
Diagnoses
The Worklist item Action '[Action]' failed to execute. The following exception message was raised: Could not load type 'System.Reflection.AssemblySignatureKeyAttribute' from assembly 'mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'
Resolution
Restarted the K2 servers