Thanks Andrea. I had though that the MBR was automatically mapped to
the the first 4 gpt partitions because that's they way it's always been
on my system. So now I wonder how it's been set that way, because I
know i've never touched gpt-fdisk and I didn't use bootcamp. Maybe the
refit installer.
I have no idea. No sane GPT partitioning tool should ever automatically
create a hybrid MBR: it's not part of the GPT spec and if it's not
properly updated at every change of the GPT table there's the risk of
massive corruption.
I know for sure that OSX's Disk Utility doesn't create one.
AFAIK the rEFIt installer just copies the boot manager on the OSX
partition and installs a startup item that makes sure rEFIt is blessed
(i.e. selected as the active EFI boot manager) at every reboot.
andrea