I was going to suggest the same thing, but since I don't use NullDC it seemed in poor form to suggest something I'm not familiar with Historically, DC games were always released in cdi (Disc Juggler) format. I don't remember the reason ATM, but there was something about that format being more compatible for some reason. Bin/cue wasn't around at that time, but if the emulator can support it, it should work.