When the Client is first installed it stores it's contacts/users directory files in the installation folder.  This folder is not writable for restricted users and read/write access is required for Jet Databases to operate.

The solution is to log in to Windows as an administrator, run PowerLog and then re-point the Directory to a location that is accessible to all.  This option is in the Settings menu > Directory Settings.

You should be doing this anyway in a multi-user environment since the whole point of the Directory is to be a shared information store.   A share on the PowerLog Capture machine would seem like the ideal place.