To the best of my knowledge, neither the BVision or CVision cards show up in the early startup menu, so don't worry about that too much.
The later libraries for the PPC hardware capture the native video and redirect it though the card so you can boot without a 15KHz monitor attached. If you can see the early startup on the monitor attached to your CVision, its unlikely to be a broken card.
Note, however, the redirection of the early startup screen doesn not depend on having the correct video drivers installed for you card.
I suspect this, or an incorrect driver tooltype/env var is where your problem lies.