R – SPWorkflowTaskProperties.ExtendedProperties aren’t populating the fields in the task

I am attempting to pass information from a task created within a workflow to its corresponding task form. Prior to the CreateTask activity, I create an SPWorkflowTaskProperties and fill it with the usual info (title, assigned-to, etc). I also add some elements to the ExtendedProperties property. However, those custom properties never make it into the Task.

I've tried setting the property key to:

• the Guid of one of my task' content
  type's fields;
• the internal name of
  one of my task' content type's
  fields;
• an unrelated name (in the
  hopes of getting the info into the
  task's properties instead of its
  fields).

Nothing works. The task, once created, contains only the built-in field values I have set. None of values I explicitly added to the extended properties show up.

The (simplified) sequence of my activities is as follows:

• PrepareTask. This is a custom
  activity that contains the
  SPWorkflowTaskProperties
• CreateTask. The task properties are bound to the one in the PrepareTask activity.
• OnTaskCreated. The task properties are bound to the one in the PrepareTask activity.
• While (task not complete)
  • OnTaskChanged

I am using WSS 3.0 SP1 and an ASPX (NOT InfoPath) task form.