Comment 1 for bug 62386

Since this still has the 'Unconfirmed' status I would like to add that this problem is well documented in every tutorial for Dual booting Ubuntu and OS X on intel macs ( why there hasn't been a bug report before this I don't know )

From: http://www.ubuntuforums.org/showthread.php?t=198453

"Grub installation fails at the end, just ignore it (you are going
to install lilo anyway)."

From: http://bin-false.org/?p=17

"The install will fail at the end when it tries to install GRUB"

http://desrt.mcmaster.ca/macbook.xhtml

"You need to use lilo, however as I'm told as GRUB makes an unsupported BIOS call."

The standard workaround has been either to use LILO ( or elilo although that requires kernel patches and since it does not use BIOS emulation, will not let you use some things like the proprietary ATI / Nvidia gfx drivers ). Or to use a patched version of GRUB AND delete your OS X partition and use an MBR instead of a GUID partition table ( which means, since you cannot dual boot OSX, you cannot install any firmware updates ).

These solutions were necessary for a while as patches were still being made for intel Mac compatibility but they are no longer necessary and some distributions like Fedora ( I have only heard this claim from others, I have never actually tried it myself ) install grub normally from their default installer with no extra patches or configuration needed on intel macs and Gentoo has documentation on how to use GRUB and still be able to dual boot OS X http://gentoo-wiki.com/HARDWARE_Apple_MacBook#Grub but I have not seen any such guides for Ubuntu.

IMHO this is fairly urgent as it prevents many mac users from installing Ubuntu.