Hello Don,
Thank you for your message.
Could you please clarify if you have the
AD tree displaying enabled in the Viewer's Navigation pane? If you do, please try enabling the
Hide default domain controller feature in the
Viewer options, on the
Misc tab:

This might be causing the issue as the computers in the tree also count against your license. So if this is the case, you are advised to add the computers you need from your AD to your address book and disable showing the AD tree in Viewer.
If the AD tree is disabled, but you're still encountering the issue, it might be caused by the Viewer configuration file (config_4.xml) being somehow corrupted (perhaps, by an antivirus/firewall software). Please try resetting the Viewer options by deleting the
config_4.xml file found in
%appdata%\Remote Utilities Files\ folder. This will reset the Viewer settings/options, your address books won't be affected by this action.
Please note that the AppData folder might be hidden by default in which case you need to enable "Hidden files and folders" in Windows Explorer settings.
Also, as it was mentioned above by Conrad and Tom, the issue might be caused by the General address book file connections_4.xml being corrupted. In this case, please try copying the address book file to another location and see if the problem still persists upon the next Viewer startup. If it does, then please try removing the
connections_4.xml file from the
%appdata%\Roaming\Remote Utilities Files folder.
Tom, thank you for the suggested workaround and for helping other users in the community.
Hope that helps.