UserApp DNContainer Control

I would like to use the DNContainer Control for a field. This works fine for OU and O Objects. But I would like to use a custom class inherited from Organizational Person Class. The Containment Flag is set on the custom class, and I have already set up a hierarchical structure of objects by this class. But even if I specify the corresponding DAL Entity in the Properties of the DNContainer Control (als Lookup and as Display entity), I cannot browse my structure. There are no subcontainers found...

The structure is within an OU, this OU is the browse starting point for the field control.

Thanks in advance.

Uwe