I did a complete uninstall/re-install of both Jack and MB and it now opens successfully. And I did this with the assistance of Harrison support! (applause
A word of caution to anyone thinking of uninstalling MB, your original download link may no longer be valid. However, it appears that it was the uninstall of MB which actually helped in my case, because I did everything else I could think of first- including an uninstall of Jack.
I really like the larger GUI. Thanks Harrison guys! As for the overall function, I haven't spent much time with it yet, but so far I'm pleased.
-SD