Bug#740504: cdimage.debian.org: Released ISO images have invalid GPT tables
my newest bug about gdisk hating an ISO with GPT and MBR is
not affecting debian-cd. (Further it is not GRUB2 specific.)
I can reproduce the user's symptoms with gdisk 0.8.1 and can work
around them by explicitely disabling multi-session emulation when
producing the ISO. This disabling is default with mkisofs emulation.
Today's debian-testing-amd64-netinst.iso shows no such symptoms
and thus should be ok at least for gdisk.
Have a nice day :)