Profile group search has no effect when profile limited to a group

I have a profile which is limited to only display contacts in the "Active" group. The profile includes a group selector to (hopefully) refine the search further ("Active" is just a smart group containing all the people in the other groups). Selecting another group however doesn't change the search at all, it still displays all the "Active" group members. The printed search criteria also doesn't change despite having selected several other groups in the profile search form:
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Displaying contacts where:

• Member of Group - Active
• Group Status - "Added"
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MySQL 4.0, PHP4, Drupal.