Oh my God! Brilliant!
I made a new install of Version B5. Copied over my old profile.json to the /User/Profiles directory. Made the simple little change suggested by Andrudis and, when I started the game, it opened up my profile without a hiccup. All of my level, experience, quests, stash items just as before.
As we all know, it's not very often that there's an easy solution, but it is SO nice when there is occasionally an easy fix.
thank you so much!
Louis