Hiya,
A couple of people have got a black screen after a config change, don't worry it's not a big deal.
All you need to do is hook it up to your TV over composite cable, that should get you into WB where you can play around with the Indivision's Config settings.
If you WB is currently set to use a mode that cannot be displayed via composite (eg you have it set to HighGFX), then boot it with a WB disk to go to PAL mode and then move the HighGFX monitor driver out of 'DEVS/MONITORS' and into storage. When you reboot your system will swap to the default PAL mode (because the HighGFX monitor driver is missing).