Dell Fax Wizard Phonebook empty for users not in Power Users group

We're using a Dell MFP 1815dn over the network from a Dell Server SC1430 running Windows 2003 Server R2 (Service Pack 2). All the users in our small office work off this server via Terminal Services. We have "Dell 1815 Fax" as one of the printers. Sending a print job to that printer opens up Dell Fax Wizard. I'm not sure which version it is -- I assume 4.02.82 as that is the version shown if I open PC Fax Settings (Start --> All Programs --> Dell --> Dell Printers --> Dell Laser MFP 1815 --> Configure PC Fax).

In Dell Fax Wizard there are two lists of contacts under the Recipents tab. The list on the left ("Phonebook") seems to be pulled from the Shared Contacts folder from the user's Windows Address Book. It can be edited and contacts can be copied to the right side ("Recipients").

This works fine if the user is in the Administrators or Power Users group. If not, the list of contacts in the Phonebook is not populated and the "Add" button does nothing. There is no error; it simply doesn't work. I don't know too much about the privileges involved in something like this. Does anyone know what privileges I might need to give users in order for this to work, with security still in mind?

Thanks!