curiouser and curiouser,
I guess a place to start would be to turn dialog on in your Open URL step so you can see what it's pulling from the field.
This is just a troubleshooting step - the process of elimination.
David, thanks for the idea. It lead me to what had happened. An employee who has layout editing permissions did not understand the table structure and changed the fields. The fields are in another table and all are blank so I guess that is how FM responds when you use Open URL with an empty string. The employees' editing capability has been taken away.
I did something similar about 25 years ago when I was transitioning from data entry to reluctant developer (FM2).