I have a Dell m4600 with Nvidia Quattro K2000M. I had some issues getting it to work. But now it works fine with VGA and Displayport (no sound through the Displayport though) But when I have the displayport plugged in during boot I get a black screen, and the laptop screen is the same. I see GRUB and then the ubuntu-boot sequence (in poor resolution) but after that it just gets black.

If I boot up without the Displayport plugged in and plug it in when I've started up ubuntu it works just fine.

It's not a big issue but if there's an easy quickfix I'd love to hear about it.