installer crashed when installing alongside os x yosemite

[bytezen]

I am installing Ubuntu 14.04 alongside OS X Yosemite and other Mac OS X systems (Snow Leopard, Mavericks).
The installer crashed and prompted me to report a bug.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubiquity 2.18.8
ProcVersionSignature: Ubuntu 3.13.0-32.57-generic 3.13.11.4
Uname: Linux 3.13.0-32-generic x86_64
ApportVersion: 2.14.1-0ubuntu3.2
Architecture: amd64
CasperVersion: 1.340
Date: Wed Feb 4 16:21:05 2015
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash --
LiveMediaBuild: Ubuntu 14.04.1 LTS "Trusty Tahr" - Release amd64 (20140722.2)
ProcEnviron:
 LANGUAGE=en_NZ.UTF-8
 TERM=linux
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_NZ.UTF-8
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Ubuntu Foundations Team Bug Bot (crichton)]

Exception during installation:
Feb 4 03:12:02 ubuntu /plugininstall.py: Traceback (most recent call last):
Feb 4 03:12:02 ubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 1770, in <module>
Feb 4 03:12:02 ubuntu /plugininstall.py: install.run()
Feb 4 03:12:02 ubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 78, in wrapper
Feb 4 03:12:02 ubuntu /plugininstall.py: func(self)
Feb 4 03:12:02 ubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 241, in run
Feb 4 03:12:02 ubuntu /plugininstall.py: self.configure_bootloader()
Feb 4 03:12:02 ubuntu /plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 1026, in configure_bootloader
Feb 4 03:12:02 ubuntu /plugininstall.py: "GrubInstaller failed with code %d" % ret)
Feb 4 03:12:02 ubuntu /plugininstall.py: ubiquity.install_misc.InstallStepError: GrubInstaller failed with code 1
Feb 4 03:12:02 ubuntu /plugininstall.py: