I have a workflow functioning that creates a user in the IDVault, with Given
Name, Surname, SSN (in a custom AUX Class) and location code (another custom
Aux class.)

Upon achieving this success I decided to try adding one more attribute at a
time to the working "Create Entity" Activity. I add "preferredName" and get
a "Workflow Error: java.lang.NullPointerException"

This is going directly from entry on the request form to Creation of an
entity.
The form field for preferredName is the same as for Given Name, or Surname.
The data mapping on the Entity Activity is the same.

Any idea what is causing this?

Thanks,

Rob.