Webmin can not find users or groups on OS X 10.5

The Users and Groups Webmin module is broken on OS X 10.5.x, probably do to some kind of change on Apple's end.

The module reports the following error:

No users were found on this system!.
No groups were found on this system!.

When Virtualmin is installed, the ability to create new servers is also affected, and it shows the following error when an administration user is being created:

Creating administration group domainnamehere ..
.. failed to create administration group!

Failed to create virtual server : Critial feature Administration user was not properly created - Virtual server creation halted.

Status: 
Closed (fixed)