Symptoms

The display form is incorrectly showing no data when it is set as the User from in the User Task (Smartforms) activity.
 

Diagnoses

If you change the form from 'Edit' to 'Display' the rule state of the activity changes. This can interfere with the way the form behaves and can make the 'Display' form show no data. If you have renamed workflows copies of rule states can be created this will interfere with the Smartform you have selected.
 

Resolution

To resolve this issue, try inspecting the workflow and see if there any duplicate rule states. If you do find duplicates try renaming the state on the offending workflow or switch it to the base state and redeploy.