Symptoms

I have restricted a picker control on the smart form to a AD Group using the method: "GetUsersByGroup".
Create a smart object with the method "GetUsersByGroup" and associated this smart object to the picker control.
But it throws error on searching for a user. The error is "The specified user does not exist."
 

Diagnoses

The first issue was that we were using the AD Group smartobject. WHile this SmartObject can be used, it is not recommended. Instead, use the UMGroup SmartObject from the URM Service. This is what K2 itself uses to resolve users and Groups.

However once we switched to the UMGroup Smartobject we were receiving an error associated with "The property yUserNameList] cannot be found." This was related to the large size of the Group and the Picker Control resolving before all of the users in the group were returned.
 

Resolution

We changed the Data Source and had it Cache the data. This way, the picker was populated with all the users in the group when the Smartform was initializing. This way the picker already had the list of users to begin with, and resolved after that.