Please try the following and see if this helps to resolve the issue: 1. Fully exit the Viewer (File -> Exit). 2. Locate the folder %appdata%\Remote Utilities Files\ and delete the file config_4.xml. 3. Restart Viewer. This will re-create the configuration file and should help with the issue.
You can try restoring your address book from an automatically created backup file as described here if you haven't removed the backup folder previously as a part of uninstallation process.