INFO: When MAC boots it looks into its whatever to findout if a directory was ‘blessed’
which means that this directory would be used to fetch the bootloader from.
Normally the file boot.efi should be there and it will be used to boot the system.
Boot from DVD, start a terminal and run this command:

sudo bless –verbose –folder /Volumes/YOURDRIVENAME/System/Library/CoreServices –bootinfo –bootefi

see this BLOG for more VERY GOOD info. Especially in the forum afterwards.