Now that's interesting. I really can't imagine what might cause that. Could you be a bit clearer on what is happening?
When there is no second monitor attached and start the laptop, do you get any screens at all before it goes dark? Make sure that your laptop is NOT hibernating but is doing a full cold boot.
If you do get some BIOS screens OK then I would say it's simply a settings issue. You have assigned the other screen as the main screen in the driver software.