I installed the newest version of Virtual Box on my Windows 10 Pro (64 bit) machine, installed Kali (newest version), and ran into the issue of Kali starting up but then only displaying a black box (after the splash screen) with a blinking cursor. That meant I couldn’t log in, as the login screen never appeared.
After trying tons of other things, I noticed that, by default, VB chose Ubuntu 32 bit as the OS. I changed it to Ubuntu 64 bit, and everything works!
I hope that helps somebody.