When WSJT-X is running, I then attempt to launch JT-Alert.  A small window pops up [Reading Settings Data/Standby] and after perhaps 40 seconds a second small window pops up with an error message [Missing or Invalid Callsign/Program will now exit].  The only option is to click OK, and the program does indeed close.

Any assistance would be greatly appreciated.

Thanks/73...  Paul (VE3PS)

Paul,

JTAlert will abort trying to start if it is unable to determine your Callsign as that controls which config file to load.
Either the necessary Registry entry is missing or your PC protection software is actively blocking JTAlert from reading the Registry key (which JTAlert creates and owns).

You can check the Registry by using Regedit and navigating to the "HKEY_CURRENT_USER\Software\HamApps" key and looking for the "callsign" entry.
eg.
  

If the callsign entry is present then you need to look to your PC Protection software as it is likely the culprit with some overzealous settings. Any File/Folder exceptions you have added will not prevent Registry read blocking, that will be (usually) hidden deep within the Protection software settings.

If the callsign registry entry is missing, you can add it (new string value).

Alternatively you can create a new JTAlert shortcut specifying the callsign. This is the method I use to test multiple different callsigns.
Simply copy the JTAlert shortcut you normally use, right-click that new shortcut, select "Properties" and edit the "Target" field of the "Shortcut" tab adding the following /callsign=VE3PS after the /wsjtx or /jtdx parameter.
eg.
   

de Laurie VK3AMA