Comment 30 for bug 774089

For this fix to work you must use the RIGHT firmware, if you copy the blog post exactly you will get the firmware for the 5,2. If you don't have a 5,2 then it won't work.

You need to find the LATEST firmware for YOUR Macbook.

For example, if you have a MBP 5,5 then I would EXPECT that you should try downloading the following firmware update package:

http://support.apple.com/downloads/MacBook_Pro_EFI_Firmware_Update_1_7_

In there there are two firmware files, for a 5,5 you want
MacBook Pro EFI Firmware Update.app/Contents/Resources/MBP55_00AC_03B_LOCKED.scap

NOTE: I HAVE NOT TRIED THIS, TRY AT OWN RISK as I do not have my Macbook right now.

If you follow the procedure in the blog post here:
http://pubmem.wordpress.com/2011/04/09/flash-efi-firmware-update-manually-on-a-macbook-51/

but using this firmware file instead then I think things should work :)

Good luck,
Who