[Zope] Local roles in Membership Product

Bill, I installed the Zope Membership Component version 0.7.8 with Zope version 2.4 at the root of the Zope object hierarchy. In has been working fine so far. However, today, for the first time, I tried to add a local role for an object. But the User Roles selection box shows no users. What a surprise, given that there are serveral users in the root acl_users folder. Is this a problem/feature/wish, or did I do something wrong? -- Loren