I decided to play around a ton (installed a 2nd LaunchBox install, that worked; tried copying over various files to see what would and wouldn't work) and ultimate found the solution.
I had to delete Emulators.xml of all things.
So I guess something is wrong with the old Emulators.xml from an old version, that the new version didn't like. Attaching it if devs wanna take a look.
Guess that means I gotta set up my emulators again. :X
Emulators.xml
The T's post in Launching into Big Box freezes on black screen/Not Responding. was marked as the answer