I have an Asus motherboard p8z68-V motherboard with an NVidia GeForce 550 Ti plugged in. The system boots just fine when I'm using the onboard graphics, but when I plug in the GeForce and use that, it won't boot. After I select the OS in GRUB, the screen goes black with a blinking underscore for about 5 seconds, then just goes totally black. Any ideas?
What version of Ubuntu? I ran into this with kernel version 3.0 in Ubuntu 11.10 on one machine, and had to disable ACPI in the boot options to get it to boot (it has an ATI card). I could (also) boot if I went back to the previous 2.x kernel, but who wants that? ;)
Apparently this is the deal (in my case anyway) until an updated driver is released for kernel v3.