I don't know what happened to cause this.

I have Snow Leopard, Ubuntu 11.04 Natty Narwhal and Windows XP SP3 on my early 2006 MacBook Pro. It is a Core Duo unit, NOT Core 2 Duo, so it is 32-bit only - Model Identifier MacBookPro1,1. I use rEFIt 0.14 for my boot menu.

For some reason neither XP nor Ubuntu would boot anymore. I'd just get a black screen with a rapidly flashing underscore in the top-left corner.

Having both those OSes failing to boot suggested a problem with the boot loader in my MBR. The rEFIT partition tool verified that my MBR partitions were still synced with my GPT partitions, so I rewrote my MBR partition table with fdisk while booted from Parted Magic:

# fdisk /dev/sda

(fdisk warns about the disk having a GPT. I press on anyway.)

p

(Print the existing partition table to make sure it's OK.)

w

(Write the old partition table back to disk. This also writes a new MBR boot loader.)

After this XP would boot but Ubuntu would not, with the same symptom. Now I used update-grub while chrooted into Ubuntu from Parted Magic:

# mount /dev/sda3 /mnt
# mount --bind /dev /mnt/dev
# mount --bind /sys /mnt/sys
# mount --bind /proc /mnt/proc
# chroot /mnt

Chroot issues some warnings about not being able to identify some group IDs. I don't know why that happens, or whether it is a problem.

At this point while I am still booted off of Parted Magic's kernel, I am running from Natty's filesystem.

# update-grub

Update-grub detects each of my operating systems then claims to complete successfully, but still won't boot.

I asked this same question over at rEFIt's Sourceforge support forum but there have been no replies yet. I also Googled quite a bit, and see many who have the same black screen problem, but none of their situations seem quite like mine.

Thanks for any help you can give me. -- Don Quixote