Are you sure about BIOS
ROM in the message? If that is the case, it means that the contents of your BIOS (not the settings, but the actual Basic I/O System code) has changed. This would mean that a re-flash (if possible) would be in order. I don't know where to get the Mackie BIOS code, I understand it is special.
It can hardly be the processor, since you're getting the messages. If the processor would be completely dead, you would get a dark screen and only a few beeps at best, if anything, at all. Have you moved any connectors (power, maybe...)?
I think that checking for any socketed chips and reseating them, and/or reseating the cards plugged into the motherboard might be an idea to try. If all else fails, try to remove all cards (midi, network, etc.) except the video card and see if you still get the message.
It is a completely different case, however, if it says BIOS
RAM in the message...
Which motherboard version do you have?