Comment 239 for bug 1289977

Comment #14 helped me. I have dualboot laptop with Windows on the first disk where the old grub was installed and the second disk with Linux partition.

The issue was that the grub on the second disk was upgraded, but on the first one, that was actually used, wasn't.

I used USB installation disk to restore grub using boot-repair and after successful start of the laptop ran debconf-show to configure grub updates to be installed on both disks.

It would be fine if grub upgrade script checked for multiple grubs and issue warning/error about some grubs not being updated if that can make system not bootable