Convert MBR to GUID Partition
Backup
Do a complete Time Machine
Boot your Leo Installer that has access to Disk Utility, Terminal and Restore from System Backup
Erase the MBR system disk
Use diskutility to create an GUID partion, putting 300mb as free space in front of the partition
Restart
Restore from Time Machine
Boot your Leo Installer and this time do a Restore from System Backup, select your Time Machine and restore everthing on the new GUID partition
Install Chameleon
Use disk utility to repair permissions
Creating ext2
newfs_ext2 -c /dev/disk0s1
fsck_ext2 /dev/disk1s2
sudo mount_ext2 /dev/disk1s2 /Volumes/boot
disktool -r
copy boot0, boot1h and boot to /Volume/boot
On your Linux
vi /boot/grub/menu.1st
title Mac OSX
root (hd0,1)
kernel /boot
boot