> (by accident I had the cable connected to the onboard video) I recall I tried once a dual monitor setup using an onboard graphics + another plugged in card. I don't remember exactly, but I think the boot message was shown one the onboard graphic card only or on both monitors. I was concerned about this behaviour then I got over it since in X all was ok.
Did you disable the onboard card from BIOS? What options do you have for this?