I've currently got win7,ubuntu and lion on one hard drive (mbr partitioned) in my laptop. However I can't boot to osx from grub2, only with unibeast usb drive. I either get 'wrong multi boot magic', or a string of unknown characters.

Can anyone advise me on this problem?!

I would be happy to use another boot loader but I need to keep mbr partitioning for the first couple of partitions (that came with the laptop, without which it won't run properly) and windows partition needs to keep the boot flag otherwise backup won't work.

Thx for any suggestions!