It's here: http://support.apple.com/kb/HT1237
As per this article:
http://pubmem.wordpress.com/2011/04/09/flash-efi-firmware-update-manually-on-a-macbook-51/
That article totally saved my ass -- good luck! :)

On 23 July 2011 16:12, Patryk Nadrowski <email address hidden> wrote:

> I also have this bug on my MB6,1... Maybe You know someone with copy of
> Firmware for 6,1?
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/774089
>
> Title:
>  Booting fails 3 times, works every fourth time after new install of
>  Natty Narwhal amd64 on Macbook Pro
>
> Status in EFI Boot Manager:
>  New
> Status in Release Notes for Ubuntu:
>  New
> Status in “grub2” package in Ubuntu:
>  Confirmed
>
> Bug description:
>  Dear all,
>
>  I am experiencing a severe problem after a new install of Natty
>  Narwhal on my Macbook Pro last night:
>
>  The install worked fine, but after reboot nothing came up except fo a
> black screen.
>  After forcing the machine off and on multiple times I was able to bring up
> the rEFIt boot menu by pressing and holding the 'Alt' (or Option) key and I
> can then boot into MacOSX or Ubuntu without a problem.
>
>  After restarting / powering off I then have to turn the computer on /
>  off the same number of times (3 or 4, I don't remember exactly) where
>  nothing happens until it works again.
>
>  I am using a MacbookPro 5,5 (13.3 Inch). My harddisk is setup as follows:
>  200MB Partition for EFI
>  20GB Partition for OSX
>  18.6 GB Partition for / (ext4)
>  108.49 GB Partition for /home (ext4)
>  1.86 GB Partition for swap
>
>  Other people also seem to experience the same issue:
>  http://ubuntuforums.org/showthread.php?p=10743955&posted=1#post10743955
>
>  This is a pretty big problem for me, so your help is very much
>  appreciated.
>
>  ProblemType: Bug
>  DistroRelease: Ubuntu 11.04
>  Package: linux-image-2.6.38-8-generic 2.6.38-8.42
>  ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
>  Uname: Linux 2.6.38-8-generic x86_64
>  NonfreeKernelModules: nvidia wl
>  AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
>  Architecture: amd64
>  ArecordDevices:
>   **** List of CAPTURE Hardware Devices ****
>   card 0: NVidia [HDA NVidia], device 0: Cirrus Analog [Cirrus Analog]
>     Subdevices: 1/1
>     Subdevice #0: subdevice #0
>  AudioDevicesInUse:
>   USER        PID ACCESS COMMAND
>   /dev/snd/controlC0:  paul       1487 F.... pulseaudio
>  CRDA: Error: [Errno 2] No such file or directory
>  Card0.Amixer.info:
>   Card hw:0 'NVidia'/'HDA NVidia at 0xd3480000 irq 20'
>     Mixer name : 'Cirrus Logic CS4206'
>     Components : 'HDA:10134206,106b4d00,00100301'
>     Controls      : 17
>     Simple ctrls  : 10
>  Date: Sat Apr 30 14:53:06 2011
>  HibernationDevice: RESUME=UUID=55afdc53-85cf-4d37-98c6-fbdd4f1c8482
>  InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64
> (20110427.1)
>  MachineType: Apple Inc. MacBookPro5,5
>  ProcEnviron:
>   LANGUAGE=en_US:en
>   PATH=(custom, user)
>   LANG=en_US.UTF-8
>   SHELL=/bin/bash
>  ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic
> root=UUID=3aad2af7-44e6-4e93-8055-7e1818600eac ro quiet splash vt.handoff=7
>  RelatedPackageVersions:
>   linux-restricted-modules-2.6.38-8-generic N/A
>   linux-backports-modules-2.6.38-8-generic  N/A
>   linux-firmware                            1.52
>  SourcePackage: linux
>  UpgradeStatus: No upgrade log present (probably fresh install)
>  dmi.bios.date: 06/15/09
>  dmi.bios.vendor: Apple Inc.
>  dmi.bios.version: MBP55.88Z.00AC.B03.0906151708
>  dmi.board.asset.tag: Base Board Asset Tag#
>  dmi.board.name: Mac-F2268AC8
>  dmi.board.vendor: Apple Inc.
>  dmi.chassis.asset.tag: Asset Tag#
>  dmi.chassis.type: 10
>  dmi.chassis.vendor: Apple Inc.
>  dmi.chassis.version: Mac-F2268AC8
>  dmi.modalias:
> dmi:bvnAppleInc.:bvrMBP55.88Z.00AC.B03.0906151708:bd06/15/09:svnAppleInc.:pnMacBookPro5,5:pvr1.0:rvnAppleInc.:rnMac-F2268AC8:rvr:cvnAppleInc.:ct10:cvrMac-F2268AC8:
>  dmi.product.name: MacBookPro5,5
>  dmi.product.version: 1.0
>  dmi.sys.vendor: Apple Inc.
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/efibootmgr/+bug/774089/+subscriptions
>