Can't run .d88 files using Neko Proj II Kai, but can run .FDI. Help

Something odd:

I have what I think are all the needed BIOS files for Neko Project II Kai, and am able to run PC-88 games file using .FDI images, but if I dare try and load a .d88 game image, I am greeted first with the boot screen and memory check, followed by a blank screen. The emulator stalls here, every time. What am I doing wrong?