Inserting that "_briefcase" directory was my only customization. In the start window everything else is default. The " "drawings" that folder is the one specified in my custom path at time of installation, which I verified from options>file locations.
I've noticed that if I try to select the other folders (templates, history), and leave it set there, the next time I select file>open, it behaves. Any other method of making the program see MY drawings directory, and it balks.
I'm goin to try to migrate everything up to a shorter path to see what happens.
If I count the characters and spaces right, and 255 characters is the limit, then the default installation was only about 3 characters away from that limit. Seems hard to believe they would allow that. I always did wonder if the long folder name "TurboCAD Professional 18" was asking for trouble.
By the way, my "_briefcase" is just a folder, and not the synchronization utility that came with some windows. That thing was scary.